The previous dash warnings were still there: ABS, Traction Control, Airbag. Then more lately I noticed random misfire at idle, and sudden loss of power during brisk acceleration or normal acceleration after coasting.

I tried to investigate with OBD devices A while ago, and before I removed the automatic transmission module, the ELM327 only found the auto gearbox missing. The ELM327 dropped dead after a few uses, and, before it died, it lit up all the dash warning lights and generated strange messages in the central display on my X350 and it immobilized the engine. The ELM 327 is now in the bin. Was quite happy with "BlueDriver" for a short while, but it only reads my X350 but not the 1995 XJR; so is the OBDlink-SX USB version. I finally settled for VCM and the ISD/SDD kit. It is a bit clumsy to set up and use, but it found DTCs which the other two failed to detect.

The Engine ECU has 10 DTCs: P1137, P1157, P0171, P0174, P0172, P0175, P1172, P1400, P1401 and P1409. I looked up the X300 DTC Summaries (it is actually for Jaguar V8 from 1997 onward), and believe they are all fuel too lean/rich, O2 sensor related, suggesting that there are air or exhaust leak somewhere, and/or possibly loose O2 sensor plugs... A few months ago I installed custom-made exhaust manifolds, and replaced the O2 sensors, so it is about time they are re-examined to identify any loose connections or air leak. Three codes were EGR related, but I am not bothered as I removed the EGR earlier to give room for the custom-made exhaust manifolds.

There is DTC C1450 for the ABS/Traction Control, suggesting a circuit or mechanical failure in the ABS Pump and/or the Traction Control Module. I have been watching for good used ABS Pump with TCl function coming up in the market, but they are getting very rare now, as only XJRs or up-market version of the X300 have TC.

There is no DTC in respect of the Airbag dash warning, but an earlier Autologic scan a few months ago flagged DTCs #14 and #51. How the VCM failed to find any fault with the airbag is somehow strange. I have found a set of good used impact sensors front and sides) with the airbag control module, but am wondering if I should replace them all for the peace of mind.

Also, I reported earlier that my memory driver seat is not moving, despite checking all motors in order, and replacing the driver's memory seat module. Now the VCM says "Driver's seat module (ERR 0xb]". I have tried two used driver seat's ECU before so I suspect that the power connection to the seat module is the primary culprit.

 

Quote
"How the VCM failed to find any fault with the airbag is somehow strange."


VCM/IDS does not communicate with the Air Bag module on X300s

 

My VCM and IDS are genuine kit. Would be weird if it does not read airbag module, when Autologic's Bluebox can.

 

Just successfully completed the Throttle and O2 Sensor Adaptations using IDS. Now all the engine DTCs are gone, with engine idling steadily at 750 rpm at operation temperature. Before that, the engine used to idle between 800 and 1000 rpm, slowly climbing to 1200 and 1400 rpm. There are also occasional hesitations of the engine at brisk acceleration, like fuel cutting out upon reaching 3500 rpm. Am wondering why this happens. The XJR has a dual fuel pump setup and the 2nd pump is supposed to start working in the post 3000 rpm area.

Meanwhile, I have ordered a good used ABS Pump with Traction Control (JLM12003). Hopefully, once fitted, it would take care of the ABS and Traction Control red light on the dash.

As for the airbag light, I have also bought off eBay a set of impact sensors (x3) together with a good used airbag control module.

 

The Jaguar documents show the 2nd pump comes on as it climbs to 4000 point and above and off as it drops under 4000 to under 3200

 

Yeh, I suppose my quote of 3500 rpm was a guesstimate; wasn't reading the tachometer when Rose lost acceleration. I was just puzzled why there was something like fuel cut during acceleration, i.e. even if the second pump has not yet stepped in, the first pump is supposed to keep the engine speed? IDS has detected no codes about this. I was wondering if it was the supercharger acting up. I heard that the supercharger spins at 5 times the engine speed....

 

Bad spot on the TPS ? Does not correspond to an exact RPM in a unsteady state of acceleration or deceleration but does in steady state of cruise . Could a weak # 1 fuel pump not keep up causing a cutback until the engine gets past 4000 were the # 2 pump recovers the engine fuel needs ?Have you looked into cleaning the wheel speed sensors ? Mine has traction control and I found the wires coming out of the actuator had deteriorated insulation and binding 2nd cable to the throttle .

See earlier reply on airbags :

https://www.jaguarforums.com/forum/x...1995-a-187218/

 

What would cause Pump#1 to cut out? If it does cut out and the engine speed is lower than the triggering point for Pump#2, the result is abrupt deceleration as at present, which can be very dangerous to any unwary tailgaters. The fuel pumps are a pig to access, so hopefully my mechanic and I need not revisit them. They were replaced new just earlier this year with the fuel tank removed and thoroughly cleaned. I also have new new fuel filter, cleaned fuel pipes, new fuel injectors, new spark plugs....

As regards Traction Control, my ABS and Traction Control lights have been on since day one, with DTC 1450 pointing to "TC Actuator Motor Failure". The brakes on all four corners have been thoroughly cleaned, and renewed with rotors, pads and caliper rebuilt kits. So what remains to be dealt with is the ABS Pump and the Traction Control Module (JLM12003 version). I hope the replacement would take away the dash lights, free it from any improper interference with the throttle, and sort out this fuel cut issue.

Thanks for the airbag resource reading. The technical guide is beyond my skills so I shall see if replacing the front impact sensor and the airbag control module would clear Code 14 and 51.

 

On the fuel pumps the # 1 my not be cutting out but may not be running with enough volume and doesn't cause a problem until higher RPMs and as you go higher the # 2 takes care of the needed volume . Might try a fresh relay for it may not be allowing enough current to pass . The rear window heat relay on the far left has the same Jaguar numbers on mine and can be swapped out . You described abrupt deceleration like a stall out vs. underperforming might be pointing to the TPS for it is a wiper arm resistor that may have a lifted off contact spot . You can see this with a old school needle meter as you sweep across the wiper length as in pic below . May not be the exact one as the X300 but gives you an picture .

There are 2 impact sensors in the grill inboard of the left and right headlight assemblies . Have you verified that the yellow sleeve airbag wire runs on both sides are connected ? The connectors on the sensors may be corroded based on their location .

 

The X300 TPS is 3 wire and can be read with a meter with the engine off at the ECU connector as you move the TPS through it's range .

Wire GY is Red 12

GB is Black 7

UW is Red 11

X300 N/A and S/C is the same.

Look for a bip or spike to high on a needle meter as resistance as you sweep it through , my not be able to see with a digital meter .

####### RESULTS #######

Paper clip into Red 11 to Red 12

Idle =640 ohms

Full Throttle = 2325 ohms

 

I have not looked at the impact sensors - I thought there is only one front impact sensor, and two side impact sensors at the sides? Will look at the sensors when the replacement sensors and airbag control module arrive. It will be good to have some spares available, just in case

As for the TPS, I would have to wait till my mechanic returns from holiday to have a look, especially to check on full throttle. Strange that such symptom did not happen before.

 

You can do the TPS sensor check with the key off and the gas pedal with the meter on your side .

The airbag wiring is contained inside the yellow covering or sleeve .

 

I did the resistance checks the TPS adjusted at 0.630 volts as I double ckecked . Adjusted to 0.601 volts now and am getting resistance readings .

 

The norm is 0.6v, I heard. Anyway, I successfully completed Throttle Adaption using IDS two weeks ago, so engine idling speed is now perfect. What do I need to tell my mechanic to identify the cause of the habitual loss of power reaching 3500 rpm? Would it be advisable to replace the TPS with a good used one be a good idea as a start? Problem is the XJR throttle is very difficult to access so I plan to leave this till my mechanic has time to tackle the supercharger rattle.

 

This is the opinion of a new person to the X300

1. TPS , since you have spent the money already to have the current TPS Adaptations using IDS the ECU is adjusted to a null signal of throttle closed . This is probable somewhere in the 0.60 volt range . Mine was 0.630 volts and had to drill out the mounting holes in the sensor body in order to twist it and clamp it at 0.601 . The labor cost to replace it without proof would be expensive on the buried SC installation so I would leave it alone and possibly look somewhere else on the engine regulation . If you were to do the easy sweeping TPS resistance test at the ECU connector and see a bad spot in the sweep then yes replace it when you can . Your current adjustment my be fine where it is for it has been adapted so your numbers may not be the same as mine and that's OK but a bad spot is not .

2 . #1 Fuel Pump Relay only , Swap with the inboard most relay ( rear window heat ) from the # 1 fuel pump relay . The relay could not be allowing enough current and the pump could not be able to supply enough volume fuel above a certain RPM . One mode of failure of a relay is called a cat whisker or pitted contact that shows voltage but low current .

3. Show the mechanic the Airbag Document Brendan McPhillips made to troubleshoot that .

4. Look for missing wire insulation on the bottom of the TC actuator and lube the cable so it runs easier and on top of that actuator you will see a followup or feedback sensor just like the TPS . Although the TC rarely actuates it may be electrically open at the null position causing a disagreement in the ECU , try tapping on it to get it to fail as you read it .

After rechecking at TPS sensor at setting 0.601 volts at idle stop

Idle Throttle = 2235 ohms

Full Throttle = 230 ohms

 

Many thanks; such wonderful guide for my mechanic to follow up

 

Update:
Air Bag - bought a full set of used Air Bag Impact Sensors and Control Unit. Replacing just the front impact sensor on the driver side already sorted the airbag light on the dash.

ABS and Traction Control - bought a good used ABS Pump with Traction Control (very difficult to find). In trying to remove the old one, the mechanic incidentally found that the connecting wires at the bottom of the Traction Control Actuator fully exposed - the cable sheath was long gone (as per Lady Penelope's suspicion in Item 4 of post #35 above) so both wires are entangled together (see picture). The mechanic traced the disappearance of the wiring insulation to the other end of the cable - evidence of what time and heat have done to degradable rubber.






This explains the dash warning as well as the earlier find that the actuator motor being faulty. Parts Number is MNA5930AA but is no longer available, new or used. Found another part number on the old unit, which reads 93BB 9U558 AF, and then found several used unit on eBay, some labelled as Ford throttle cruise control unit. Ordered one and see if it would sort the ABS and TC warning light.

 

I plan on drilling out the spot in the red circle to remove and replace the wires . With some penetrating oil and some heat it might spin off . Then at a muffler shop I will have them spot weld it back .

 

Yeh, my mechanic planned on doing that too, but advised that it would be much safer having a spare available just in case the drilling fails or the inside is beyond repair. The one I bought cost only GBP 8, with original wiring looking good.

 

While you're up to speed and in the area you can read the wheel sensors as a basic resistance of 1300 ohms at the module connector in hand . Grouped in pairs as colored in pic . The sensors face can be removed and cleaned yourself without jacking the car as they get dirty and cloud over blocking the rotor signal .

While you have the ABS module with plumbing out there is a common history of a soldier joint going bad inside , you my not want to go back and remove it again , simple repair . You can use a round hole saw at the precise spot for less mess . File below pic