When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Would really appreciate some advice re a possible TPS / TCM issue?
I eventually found a Technician that have the VCM / 131IDS & SDD setup! (contact me for details if living in or around the Cape Winelands). Unfortunately there is no Jaguar / LR Dealerships down here that can “properly" communicate with the 1995-1997/ AJ16 cars. Trust me Ive searched far and wide.
I had the "Throttle Pot Adaptation" done and also erased all the old fault codes. Put it through some drive cycles and then performed the 100-00 Complete Vehicle Test.
IDS then showed an error under Transmission Control Module (ERR 0xb), when opening it showed E003Throttle Position (Transmission Control Module) showing no Voltage. Please see pictures below.
Tried researching the E003 error code to no avail..,
We (the Technician and I) concured that the first thing should be to establish proper communication. In hindsight I should have actually asked for some more “live data” testing as my Autel scanner does show my TPS being in spec - Idle 12.2% - WOT 91.5% and moving as pedal are depressed.
I then found an local Indy with a good Bosch oscilloscope to back probe from ECU to the TPS. We did a sweeping test and all seems well with no dead spots and a very smooth transition .., again shows the same V / % at idle (0.65V) and WOT (4.5V). The test wasn't performed while driving the car and think only on a cold engine.
So now I am not sure what to do next? The TPS are one of the more expensive parts and I am not even really sure if it is the sensor and or the ECU / TCM? I had some corrosion inside the ECU connector pins (water ingress) years ago but was rectified ..,
Had anyone ever had issues where a TPS / Wiring tested all good but then actually were not?
I have the following symptoms that could be a faulty TPS:
intermittent start and stall (stalls about 60-70%of the time). If I feather the pedal it will always start especially if I keep the pedal depressed for a few seconds. Almost feels like the engine is suffocating before stalling.
slightly higher, and oscillating rpms at idle (P) 820-930 rpms. Should be around 750 rpms.
slight rich running STFT
LTFT were stuck frozen until the recent TPS adaptation and now at a more reasonable and sensible -5.5 on both Banks.
Ive pretty much changed or checked everything else except the Camshaft Sensor, IACV, and TPS. No air leaks that I know of.
Other than that my car runs perfect when coming of idle ..,
-5.5LTFT is neither reasonable nor sensible and I suspect you look at that as a problem.
1. When was the last time the oxygen sensors were replaced?
2. Any chance the MAF needs to be cleaned?
3. Have your injectors ever been serviced/cleaned/replaced?
4. Can you pull the small hose to your fuel pressure regulator and tell me if it smells of fuel?
5. When was the last time you replaced your fuel filter?
Based on your stall comments, I wonder if your injectors are leaky, and/or your fuel pressure regulator is failing?
Thanks very much for the reply .., always appreciated.
Yes I had the same thinking process .., (guess spending lots of time on the forums :-)).
Oxygen Sensors: About 2 1/2 years ago NGK 25018. Luckily only have 2 and not 4 like other Countries (about 4000 km with them so far).
MAF: LNA1620AA have recently replaced (drilled out rivets and cleaned properly with CRC MAF cleaner - didnt make much of a difference though). Maf readings slightly higher than should be 8-9 g/s @ idle but I have custom headers / downpipes and a slightly more free-flow exhaust system. Also my idle in (P) are higher than normal 820 -930 rpms. Do have a spare MAF and have almost identical readings.
Injectors: had it done about 3 years ago and pulled it out again a year ago to double check on previous work. Tested good under various pressures and definitely not leaking / dripping. Might be a very small volumetric difference on 2 of the 6 but not sure if it is enough to give any of the above issues?
FPR: have checked and all good. (Actually have a permanent Fuel Pressure Gauge fitted to test FPR and Fuel Pump / Fuel Rail functionality). Think around 41 Psi at the Fuel Rail before Injectors. Dont think its a Fuel Pump issue either.
Fuel Filter: replaced 12 months ago (backwashed the old one and looked very clean. So no problems with Fuel Tank corrosion / dirt either)
Crank Position Sensor: recently replaced
Ignition Coils: recently replaced all six and have some spares that I also swopped out for testing.
Spark Plugs: Champion RC12YC (gapped correctly = 0.9mm / 0.035 inch) replaced a few weeks ago just to make sure!
Air Leaks: Checked and none that I know of?
Throttle Body still looks surprisingly clean..,
IACV: when removed had some gunk but was cleaned by a Mechanic 2 years ago (thinking of going under the car and checking on the IACV & TPS this coming week).
TPS: testing alright with Oscilloscope (0.65V / 13% @ Idle and 4.5V / 90% WOT). Sweeping test looks good no flat or dead spots with smooth transition between idle and WOT.
Battery: Newish and still in good shape.
Checked and cleaned most plugs / connectors.
Gearbox Wiring Loom replaced (damaged when Transmission mounts were replaced).
As mentioned my LTFT were "locked" at - 11.8 for months until I performed the Throttle Pot Adaptation (via IDS / VCM) and within a few kilometres changed back to - 5.5.
The -5.5 LTFT I have had for a long time even before I started doing all the above replacements & tests it only went to -11.8 when one of my MAF's started acting up (eventually threw a code P1178 - "Adaptive Fuel Metering Trim too Lean" before it completely went belly up! Replaced the MAF but my LTFT were frozen until performing the TPS Adaptation and almost immediately went back to the -5.5 LTFT as before ..,
Vee: If I remember correctly you had your TPS replaced and it fixed your LTFT? You weren't sure if it actually was the sensor and or just the crunchy wiring harness from the ECU to the TPS that you ended up redoing after your LTFT started going South.
I recently acquired IDS 118.05 software through a very nice member on here and in the process of installing it on a old Dell Laptop with Windows XP Pro (SP2) which I am still having some issues with but hopefully will be up and running soon. Then its finding a genuine working VCM which I might have found but still needs to test properly when PC issues are sorted ..,
As things stand now I don't know much about IDS and really don't know of anyone locally that does either. Even had a look at the online manual for IDS /SDD but couldn't find what I was looking for.
As mentioned before when we recently done the 100-00 Complete Vehicle test it gave an error under the Transmission Control Module and when going into that it just said E003 Throttle Position (Transmission Control Module), but my Autel’s & Bosch Oscilloscope TPS readings seems to be ok? I will probably go back for another round of tests with the IDS / VCM and this time try to pull some more extensive "live data". Will also give me the chance to perform the Oxygen Sensor Orientation that I skipped the last time as mine were mixed up for a few days after downpipes / headers were installed years ago .., actually prompted me to buy a Diagnostic Scanner and quickly saw that my STFT (-25 Bank1 and +25 Bank2) were totally wrong! Ive read that some members believe that mixing the O2 sensors could possibly contribute in “locking" the ECU.
Question re IDS: Does Throttle Position always fall under Transmission Control Module (TCM) in IDS? I would have though it would be under the Engine Control Module (ECU) as all the wires from the TPS do connect to the ECU. I do realise that the TPS are crucial in the functioning & operations of the TCM but wondering if IDS is giving me a clue where to possibly look? My car is running & shifting well just the intermittent start & stall issue accompanied by the slightly higher / oscillating rpms @ idle and the -5.5 LTFT.
The intermittent start & stall issues have been ongoing for about 5 years now. Some days better than others but on average a 60/40 split. But will always start if feathering the pedal and keeping it there for about 2 seconds. It does feel that the idle has slightly gotten worse (more wobbly / higher / oscillating) over time. The -5.5 LTFT have also been there prior to all the work done above or since I have acquired an Diagnostic Scanner .., Dont drive the car that much but would really love to get this fixed now!
I realise there is a lot of moving parts here especially on older cars trying to diagnose symptoms but hopefully there is a IDS Guru that could either shed some light or point me in the right direction re the IDS readings ..,
Sounds like you have everything in check. Any parts I would have asked about, you have addressed...except that Fuel Pressure Regulator, but that is not a common problem...overpressurization could result in a negative LTFT though...
The only thing I can offer is to start the engine, drive it till it's warmed up and, with the engine running, disconnect the TPS for a few seconds, then reconnect it. Don't burn yourself. I can't tell if this has helped "reset" things for me, as I tend to make the mistake of having other repairs/changes made, but it seems to be somewhat consistent...enough for me to believe that it does help.
I can tell you that I did swap out the TPS (after swapping out every other part on the car, related to the idle) and even though the TPS bench tested just fine, the new TPS fixed my LTFT problem of 10.8%.
I can't help you with your IDS problem. Motorcarman may now alot more. Perhaps he'll drop in here.
The E003 error is not an error with the TPS per se, it is flagging a comms error from the VCM/IDS to the control module - so it cannot provide the data you have requested. You would see the same E003 if you had looked at any of the Trans module PIDs at the same time. Your first screen is also showing a comms error to the Trans module.
From the tests you have done with voltages from TPS and running the TPS Adaptation, then I would suggest your TPS is fine and would put it at the bottom of your worry list.
I also think LTFT of 5.5 is absolutely fine and will definitely not cause any issue with normal operation of the vehicle. Not something that I would even be looking at.
BTW - if you're struggling with XP, then IDS 118.5 will run quite happily on Windows 7 Pro (but must be 32 bit version).
No need to get under the car to access the TPS, you should be able to reach in there by hand...it's tight, and you might have to work by feel, but its doable.
My 96 XJS is running now at -0.8 LTFT on both banks. Personally, I believe -5.5LTFT is not great, but yeah, you should be able to drive with no serious problems. I don't believe that these engines stray that far from 0 LTFT, even over time. My engine has over 135,000 miles on it now, 75,000 of those miles were driven by me since 2014.
Yes the Technician (IDS / VCM) said he reckons it is a communication issue with either the TPS to ECU and or ECU to TCM. Basically I need to try and figure out why my car isn't communicating properly!?
b1mpc if I understand correctly it could also be the IDS / VCM being at fault and or my ECU or TCM I need having a closer look at?. And that IDS normally should be able to communicate perfectly with my Transmission Control Module (TCM) - not showing any error comms?
I at-least have established that the TPS & wiring to the ECU should be good but just not sure how the ECU are interpreting the data.
As mentioned before I had my Gearbox harness to TCM replaced due to stretching / breaking up some years ago while replacing my rear Gearbox mounts .., so immediately went back to the shop that done the work after the IDS diagnosis. They are very confident that its nothing to do with them .., actually willing to bet their house on it :-). My shifting is very smooth since the loom’s been replaced and don't have any drivability issues that I know of?
Yes having some issues with Windows XP Pro and might just give Windows 7 Professional 32 Bit a go as is more readily available ..,
Will give it a go from above .., didn't think it was possible with the SC but let's see?
I am also not convinced my IACV are 100% and might just be the next sensor to having a closer look at!
Yes I also bought my XJR around that time 2012’ ish. And now have around 160 000km on the clock. I dont see too many over here so find it difficult at times if something needs to be fixed .., luckily I have learned a lot from these forums and really appreciate all the advice and knowledge being shared!
You have 2 speed sensors in the GM transmission to the transmission TCM so the engine and transmission can and do talk to each other as they coordinate shifting / engine regulation
This looks away from a TPS issue which you have addressed as best you can and my vote is that it's fine as well
Could be a simple on the transmission connector cleaning
Someone did find the connector on the TCM itself loose
There is the carbon buildup on the SC engine version valves , Good hard run Italian tune up ?
if I understand correctly it could also be the IDS / VCM being at fault
Yes that is most likely. I've had a VCM/IDS set-up since 2009 and have seen the comms errors seen in your pictures on a regular basis. I always put it down to my VCM and/or the IDS software rather than an issue with the car. We have to remember it's very old technology and IDS itself was just an updated version of the even older JDS so at the time was leading edge stuff I think.
If you can read the TPS and other Trans stuff from your Autel scanner then forget about the IDS issue, and forget about a TPS issue.
Your list of checks is very comprehensive. A couple of other things to check not on your list
- Throttle clearance when closed. There should be a small gap (5 thou rings a bell but please check this)
- engine earth strap cleanliness and security
Hello Z55, Looking at the code that you, Did you know that ERR003 means ERROR in communications of the pertinent circuit. If you have used a ohm meter on the circuit to the point of exhaustion, Then there is only two things I can offer. Rent or purchase a low pressure smoke machine and test the intake and exhaust manifolds for leaks. I have a 1995 XJR TCM you can have for the price of shipping to you. I would do the smoke testing first then the TCM.
Your current issue although hard to figure out gives you few pointers.
The intermittent stalling might be due to faulty MAF, cleaning it doesn't always fix it. Depending on the year of the car, early cars can be started without MAF plugged in, later cars can not so if you have a later car, start it and then disconnect MAF, see how it performs. ECU will default fuelling but if MAF its at fault - car will drive absolutely fine. if you do have to replace it, go for one for Rover P38, they are the the same MAF and are fairly cheap and good quality.
Your oscillating revs and a higher idle can point to three things. Issue with TB setup(gap too large, should be 0.002*), faulty iacv(not closing fully or oscillating) or air leak.
TB setup is pretty obvious, especially if you have access to IDS, clean, set everything and do an adaptation. Faulty IACV can be a pain to diagnose, you could check its operation with the TB off the car, when switching off the car, IACV should extend fully(close TB) and then after a second or two go back few steps to park position. You can test the car with IACV in fully closed position and in park, just need to know when to unplug it.
Air leaks can be a proper pain too and are hard to find unless you have a smoke machine and can pressure intake slightly. I would check compression in each cylinder first. This will check for possible valve issues and possible air leak from injector seals, since you had them off so many times that could potentially be your issue too.
I would also inspect possible intake manifold gasket air leak. I could never diagnose this without actually taking the manifold off but this was an issue few years back on mine. Not a difficult job though.
You've not mentioned CTS reading either, is this correct and in range?
Is your linear switch operating ok and can you see the light switching between the gears? Reason I mention is that you replaced your gearbox loom, RPMs are tied on some way to the gearbox position, you can see this happening when you start changing gears, from N to D, even tiniest move up from D to N have an effect on RPMs and if that signal is breaking I suppose you could have oscillating RPMs(however unlikely that might be).
Checking TPS is relatively easy, you can do it with OBD and live data(or oscilloscope), just record the readings over some time while driving and see if the signal is constant, if it breaks even for a second then this could potentially be an issue.
Just to make sure your fuel pressure and supply are fine, temporarily pinch the rubber fuel return line under bonnet and see what happens.
Last thing I would check is the inside of the ECU for possible damage, you can see mine here for a few years ago:
Will have a more thorough deep dive into the TSB, Speed Sensors and Transmission Connector.
When I first had transmission shifting issues (herky jerky / late & sudden engagement) after back transmission mounts were replaced - I took my car to the best known auto transmission shop in my Province (30 plus years of experience) .., waited for months before they took me in but at-least gave me time to do more research!
First thing done of course was to scan for any fault codes at the Transmission Shop. I will list them here for it might be of help for someone someday ..,
P0713 Transmission Fluid Temperature Sensors high input.
P0743 Torque Converter Clutch System Electrical.
P0748 Pressure Control Solenoid A Electrical.
P1796 Kickdown System Malfunction (think I sorted that out myself by adjusting the switch under the Accelerator Pedal for greater TP opening).
notice that the first 3 codes all connects to the Transmission (Electrical Guide).
So after having done extensive research while waiting on my turn I specifically did mention about the “Red Herring” re that of the transmission loom breaking and or stretching inside of the transmission connector plug .., I could see the Master Tech didn’t took the advice too serious, said they will probably start by first testing and then replacing if needed the Pressure Control Solenoid A (which they then done). Workshop reckoned it could possibly be the suspect part and its probably a good idea to just change it anyway as they dont last forever.., also serviced the Torque Converter, Transmission Fluid change and a few other things ..,
Needless to say that didn't fix my problem(s). After almost 5 months I contacted only to hear they cant seem to find the fault. Actually struggling to establish proper communication - Thus I printed out almost every writeup and fix I could find about the transmission wiring loom and emailed it to them. Also just for peace of mind I pulled the ECU & TCM for some testing at a well known ECU Electronics Shop. I previously also had the dreaded water ingress corrosion to my ECU which had to be cleaned - that also gave me weird starting & shifting issues.., this time the ECU looked perfect by eye but took it in anyway. The ECU tested ok but the TCM apparently had some "electrical noise" which apparently then been rectified .., The owner of Electronics / ECU shop didn't believe that it would have caused me my current shifting issues .., Long story short 2 months later my car was back on the road with smooth shifting!
In hindsight I'm wondering what did cause the "electrical noise" in the TCM and if that could possibly be the problem with IDS / VCM not being able to communicate with the TCM? especially the Throttle Position .., or could it be that the TCM is just having some minor issues re the data collection from the Throttle Position? (Parker thanks for the Electrical Guide had spent some time going through it and found it very helpful).
Will also have a look at the TCM connector.
Yes Ive read about the carbon buildup on the exhaust valves and engine valves. Some of the local Jag Technicians keep on telling me I will never get my car to run perfectly due to the quality Petrol being used and that these cars were build for overseas (different fuel and a different era). I don't know if I believe that as I had times where my car’s been running very well. But yes an "Italian Tune Up" might have to be done soon. Any suggestions that you found have worked for you and or others?
Yes thanks for that .., I am going back for another round of tests with the IDS / VCM as I would like to see if my Laptop with Windows 7 Professional (SP1) will now be able to communicate with a working VCM. Had some struggles with Windows XP Pro (SP2) regarding activation etc. Plus will be doing the O2 sensor orientation while I am at it. Dont think I have any problems there but might just as-well as I had it switched for a very short time long ago.
My specific Autel scanner unfortunately doesn't have the capacity to read TCM data but does the ECU (TPS, MAf, O2, STFT, LTFT etc). Might have to find the more advanced Autel MaxiSys that the Transmission Shop used that can tap into the TCM codes / parameters. Then I will know better if IDS / VCM error comms could be ignored ..,
Throttle clearance when closed should be ok or at-least that was what I was told by my Indy Jaguar Mechanic (30 plus years experience) but worth to double check.
Haven't checked the engine earth strap yet but will add to the list of things to do ..,
Yes thanks Larry b1mcp also pointed that out to me but thanks for confirming re the comms issue. I do see now in the Electrical Guide that the Throttle Position does link up and go to TCM (input). Is there an easyish “bulletproof” way in testing the integrity of the circuit? I might not be able do perform it but then at least take it to someone with the right tools providing them with the correct instructions.
Will have another go at looking for leaks - even though we (myself and various others) have searched for leaks and rectified when founded but maybe it's time I do a full blown low pressurised smoke test. Have performed one recently myself for only the inlet tubing before and after the Maf but could have been more extensive ..,
Regarding the TCM I might just take you up on your very generous offer .., what serial model / number TCM do you have? would be much appreciated but before confirming let me first conduct a electrical integrity test on the TCM (Throttle Position).
Going for one more IDS scan this coming Friday to just make sure what else could possibly be seen on the Transmission side of things. Larry do you know if I can perform and re-flash and or reprogram an old or new TCM unit? Ive read somewhere one might need to reprogram these units especially if getting a new unit? If so is it something that IDS could perform?
I do have a hunch that my TCM might be the culprit as when I had it looked at by a reputable ECU / Electronics shop the owner called to find out what exactly were wrong with my car cause he did pick up some "electrical noise” from the TCM but after hearing the symptoms (transmission harness saga; herky jerky shifting from 2 to 3, sudden / hesitant engagement / lockup) he reckoned it should not be the issue. Again in hindsight I should have asked more questions at the time.
Maf unplugged before starting: Car will crank and take .., but wont keep running unless I keep my foot on the pedal as soon as I take foot off pedal engine will stutter and die.
Maf unplugged engine running: dies immediately even when slightly feathering the peddle.
It could very well be that both of my Maf’s are slightly out of spec .., dont have a new and or other unit to compare it to? as mentioned above Maf @ idle can range between 8-10 g/s. Dont know how much difference a more free flow exhaust system (custom headers, less cats) could influence the Maf? Some knowledgeable members even question the accuracy of the readings seen on the scanners?
I have the XJR SC Maf though (LNA1620AA) thus if I remember correctly the Land Rover P38 wont work on mine. Will work on the N/A x300 / AJ16’s though (LHE1620AA). Really wish it would have worked on the XJR’s because the price & availability is soo much better!
(1) Gap (TB) Think is still ok but will double check,
(2) Leaks: Ive been very fastidious about any but you never know, probably just have to do a proper smoke test as suggested by you and others, especially the valves, injectors seals and even my custom headers / downpipes which might need tightening again.
(3) IACV: thinking about maybe just replacing as its not the most expensive part and to get the TB off of the the XJR is not a 5 min job .., I will just go from underneath maybe remove the Oil Filter for better access. Actually had a Mechanic in a while ago and he mentioned about all the gunk that he had to remove from the IACV. Unfortunately it didn't make any difference in the intermittent start & stall issue. Idle was still not perfect but closer. Do you know if one can access / clean the “air bypass passage" without the TB removed from when under the car (XJR)?
(4) CTS: Shows good on my scanner - also checked by a Jaguar Technician not too long ago and seemed fine.
(5) Linear Switch: yes have actually replaced it almost 8 years ago with another good “used” one - done at the same time as my ECU had water ingress / corrosion. But good point. Actually my Sport / Normal switch button's light doesn't illuminate anymore (the one on the bottom of the Gear Lever console and not the SPORT MODE on the Instrument Panel that does come on. The SPORT function does work) and cant recall when exactly it happened (does feel around the same time as I got my car back from the Transmission Shop but not 100% sure?). The lights does switch when going through the gears .., only struggles with the (N) and have to wiggle it some to eventually make proper contact (light illuminating) will also then experience a very very slight change in rpms.
(6) I do believe TPS is good now after extensive testing - just not sure what ECU do with the info? will have to open up my ECU. Unfortunately the Transmission Shop guys put a very sticky substance (looks like Silicone) around the connector plugs! I specifically asked for Dielectric Grease (keeping out any possible future water / moisture).
Question: how to go about removing such a substance (Silicone) without damaging the pins / plugs?
(7) Have also done the pinching of the fuel line when I installed the permanent Fuel Pressure Gauge and didn't find any associated issues with that either.
(8) ECU’s inside: yes might need to personally have a look but have had it twice already at a ECU specialist shop.., did see the pictures of yours. Goodness me! Glad you found the problem.
I definitely have some homework to do! might keep me busy for a while but hopefully will find the fault(s) sooner rather than later ..,
So I believe I might have two separate issues:
(1) Throttle Position communication error either on the ECU, TCM and or the wiring between the two? will hopefully soon know for sure after some more testing.., find it interesting that my shifting seems fine and surely that wont have any influence on my other issues eg: Start & stall and idling.
b1mcp theory could also stand true but will hopefully know soon if its just down to old IDS / VCM hardware & software glitch in communication.
(2) I have the intermittent start & stall. Slightly rough & oscillating idle on coldish engine. When car is nice and warm after about 20 min driving the rpms increase and the STFT (+6 to +10) have to adjust for a slightly leaner condition.
Over the weekend I had a good run and noticed the following:
Cold start @ idle (P): 710 -760 rpms in Closed Loop (IAT: 15-25C) STFT -5 to +1
Warm / Hot Engine (after 20 min drive Summers day) @ idle (P): 850-930 rpms (ECT: 90-93C) STFT +6 to +10
Aircon & fan on max @ idle (P): 730 -760 rpms (warm engine / 20 min drive).
Aircon switched off but fan on max @ idle (P): 800 - 850 (warm engine / 20 min drive)
Aircon & fan both switched off @ idle (P): 850 - 930 (warm engine) STFT +6 to +10
When in (D) always around 650-690 rpms Hot or Cold Engine.
When just normal highway cruising STFT -3 to -15.
Does lean out considerably when moderate acceleration under load on highway STFT +2 to +7
LTFT: -5.5 both Banks (have been staying constant since after TPS Adaptation performed).
So if I either switch the fan, aircon or both on when car nice and hot my rpms drops slightly .., could this possibly point to a faulty IACV? mustn't the idle adjust and be kept constant if IACV working properly?
Also the leaner STFT @ idle (P) when at operating temperatures (after about 20 minutes driving / warm Summers day) could this either mean an air leak which get worse (thinking maybe exhaust downpipes) as the car heats up and or a sensor that becomes more problematic / erratic at warmer temps?
Maybe this info might help point to something more specific and concrete?
10-13-2022, 08:49 AM
TPS / TCM Issue?
