OK I have a problem that is driving me bonkers, I have randomly gotten the weird trans codes, sometimes it would go into limp mode, sometimes a semi limp mode which will just lock out 1st and overdrive, and then lately its been P0758 and P0753 which I know are solenoids A and B. I read alot of other peoples expriences and tried followin suit to see if it would help. I normally could just turn the car off and clear the code and it would be fine for a while. But I recently last day and half cant get the codes to go away, I changed the trans fluid an used mobil 1 and new filter, installed new trans mount with new springs and isolator, took off all the trans connections and dielectric greased them, the internal wiring harness in the trans looks like its been redone nicely and seems good, I changed the solenoids both A and B with new ones from GM, I have checked the fuse in L heel board #14 and its good, and I checked the 5amp in the right heelboard and its good too but cant get the codes to clear. I ordered a new external harness from Jag but dont want to have to do it if thats not the cause any ideas would be great. Hate trying to drive around with only 2nd gear and reverse.

Car is a 1995 Jag XJR

 

It is difficult to diagnose a mystery problem like this online. It appears you've done everything you can mechanically, and assuming it was all done correctly, you're back to electronics - cables, harnesses, connectors. Often faults lie here and go undetected until the last ditch efforts.

One step that you did I'd highly encourage you to reverse is the dielectric grease on the harness connectors. This is not necessary and very well could be contributing to the problem. Dielectric grease works OK when talking about high voltage and high amps, not low voltages and miliamps.

If it were mine, I'd flush the grease out of the connectors using something like a brake cleaner, then let them dry out, follow up with an electronic contact cleaner, then reassemble the connectors dry. If you replace harnesses, same thing, make sure all the grease is gone from the mating connectors.

This will spark a big debate, but trust me on this one.

 

Thankyou steve I will give this a try today and see how it goes

 

I am not a transmission expert but the way I read your post I am not convinced that the application of Dielectric grease is your problem and since you had the problem prior to applying the grease and leads me to believe it is not the issue. I would be directing you to lose connections and the possibility of a poor connection in the trans control module. I am send you a oneline for your 1995 xj http://www.gusglikas.com/images/Auto.../jagxj1995.pdf and if you look on Fig 5.1 it might help.

This is not for your year car but might help http://www.gusglikas.com/images/Auto...%201997-99.pdf

You should check with Jaguar. It seems that the trans for that car 4L80E Vin # 720001 – 812255 had a service bulletin regarding the control module. I hope this helps.

 

Good stuff gus. And a shout out from roanoke. I know winchester is north, but we like you anyway.

 

Thank you Gus I will definitely be looking into that as well today and will be letting you both know how it all goes

 

I agree entirely with Steve 11 about contacts. A proper contact cleaner such as "Electrolube" is the best in this application.
The battery question keeps coming up involving random errorcodes; there's no doubt an old or unsuitable battery can upset the microprocessors in Jaguars, even if the battery can swing the engine well during cranking. The reasoning is not clear, but the facts are there. With my 2006 S-typeD, wiring a large electrolytic capacitor across the battery (original Jag.) appears to have stopped a random "restricted performance" message in window. I'm not saying it will cure your problem, but it's so easy and cheap to do it's worth a try. I think it might be an idea to clear the codes with a suitable scanner as well. Good luck.
Leedsman.

 

After reading about Electrolube and CRC products I see a remarkable resemblance between the two only the term Dielectric is not used in Electrolube it uses lubricant. I guess it is in the interpretation!

 

well I am getting my new trans external harness today and will be installing it and cleaning the grease off and just making sure its a ice strong connection. The connections on the TCM looked good so far and since it has new solenoids, new fluid and filter, and a new trans internal harness dont think it could be anything else besides the external harness. Not to mention when I was doing the trnas mount I did pull down on it a bit cause I thought it would give it a bit more slack and then bam this all started it went from intermittent to constant LOL.

 

Thank you leedsman for the thoughts I have a brand new battery in the car so it shouldnt be causing any issues.

 

K guys strike 3 im OUT I am at my wits end Im not an electrical guy my mind works mechanically and I have done all I could think of external harness, nw solenoids, checked all fuses, trans has a new remanned internal harness, and I have looked at my connections on the TCM and everything looks ok what can I do need this car running properly so th wife dont kill me soon.

 

Also checked pins 43to 53 and 39 to 53 pins on the tcm connector and got 20.0 to 20.4 on both so the solenoids are getting power there. come on guys I feel we are so close that I can taste it LOL Im starting to wonder bout the internal wiring harness I didnt do it it was already done but it looks good its all new looking but that dont mean crap I suppose. So throw some ideas cause Im out of any lol

 

XJR-0220,

The diagnosis on these solenoid codes is really pretty simple. It's either a failed solenoid or a harness issue. If you're sure about the condition of the solenoids (you replaced them new, right? Because these are notorious for sticking), you're now left with harness connections. If the internal harness is all that is left, I would be pinning it out (continuity test) or replacing it if that is all that is left.

Were you able to get the conectors clean...very clean? Use a "no-residue" electronics contact cleaner like CDC.

 

Brand new solenoids from GM and I cleaned the connectors very well I think I will look at them again today LOL I was looking at the jag diagrams and it shows on one that it has a relay for switched ignition power and one doesnt or would I rule this out because I have voltage at the tcm?? Also with the help of Gus we have seen that on the GMs the ignition switch can be the cause but havent seen that on the jags yet any thoughts??

 

An the weirdness keeps a happening well I went out today to start doing some more diag work and when I pulled codes I got a p0743 no longer am I getting the p0753 or the p0758 and I drove the car. Sure enough I have all 3 gears but no torque converter engagement. hummmmmmmmmm

 

Ok opened the tcm an it looks brand new it has zero corrosion and looks new inside, checked pin 55 and has 12.64 volts 53 has zero when ignition is off turn it on and it has 12.63 and pin 54 has a good ground back to square one LOL. Still wondering if its the internal harness even though its been redone it may have been done wrong or they may not have gotten a solid connection for the wire that connects to all the solenoids just weird I get the 2 codes forever p0753 and p0758 and then after harness change and all it goes too a p0743 and the other 2 codes are gone maybe I didnt clean the contacts as good as I thought I will do that next and report back what I find. Also did a hard reset by touching the batt cables with no change opened my mode switch to see if there was any corrosion i there and nothing there either cleaned the contacts and reassembled and still has same p0743 code.

 

Ok checked the internal wiring harness and its not super bad but not great I fixed anything I could and installed a new TCC solenoid just to have the new upgraded part and then drove it and it drives fine but the TCC wont engage and the trans light stays on evn after clearing comes right back on and gives P0743 so ideas would be great at least its not the p0753 and p0758 lol

 

process of elimination is what I am doing now I took out the internal wiring harness and corrected all the crappy soldering and bad heat shrink. I had a small epiphaney when I got rid of the codes P0753 and P0758 it was after I dropped the pan and was messing with the wires and where they were bunched together I found the main wire that connects the 2 solenoids was kinda glued to another wire where the solder and thin heatshrink was. I seperated it from each other and then the code disappeared. So just to rule out the internal harness I dropped the trans and removed the whole harness and noticed that the TCC wire was also glued to another making me think that the wires were shorting each other out. This is just a thought but hey anything is possible. I removed the had soldering and added aircraft quality double butt connectors and after connecting them I added some good solder sealing the connection. Then on top of that I did 2 layers of quality heatshrink and then did a resistance test through the wire to make sure that it had a soldi connection and all were perfect. Gunna reinstall it today and then I will have eliminated another possible source if the problem is still there. After that it would have to be futher up in the harness somewhere cause I have so far replaced all 3 solenoids A, B and TCC, new external harness, checked the TCM opened it up and looks new, rebuilt and checked internal harness, and only thing left is an open circuit somewhere from where the external harness connects to the TCM. Wish me luck that this internal harness works guys

 

well seems that was another failed attempt and not understanding what the hell is going on so recap new external wiring harness from trans to center console, new solenoids shift A, shift B, and TCC, rebuilt and checked internal wiring harness, opened up tcm and looks brand new no water, no corrosion, it literally looks brand new, checked all fuses (good) not getting the p0753 or the p0758 anymore just getting the p0743 which is a torque converter not doing as commanded. Checked pins 42 (tcc) and 53 (ign pwr) and suppose to be 10 ohms and its nada so open circuit somewhere. But WHERE!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

 

XJR220, do not be disheartened, you are doing things the right way; in a car, everything has to be shipshape and Bristol fashion otherwise it will fail under stress just as in an actual ship/boat.
I know a bit about the torque converter clutch having learned the hard way but with the great assistance of this website. If your XJR uses slipclutch in the box, read on. If it doesn't, it's just informative. A slipclutch is under special solenoid control by the transmission microprocessor. It's not a simple in-out jobbie; the solenoid can be used in a "partial" mode so that the TC clutch can be deliberately slipping. This slipclutch idea is used when the car is going up a slight incline in the lower gears and the TC itself otherwise would be in full use. The idea is to save a bit of petrol/diesel under these conditions, partially reducing TC losses.
How is the "partial" control of the actuating solenoid achieved?
It's called pulse width modulation, PWM., a familiar idea to any electronics engineer, to be found in every home inside the tv and computer.
Prior to PWM., to control a motor, lamp, solenoid etc., you had to use a big variable resistor, hand controlled and VERY lossy. You might still find these in operation in old-fashioned trams, the driver having a big handle to operate and control the 600volt dc. to the traction motor. It was a bank of switched resistors of high wattage.
This is no good to a microprocessor. The power supply is switched on and off very rapidly indeed by an electronic switch. 150,000 switchings per second is typical. So the switching rate is 150KHz. More than this, the time interval when it's "on" can be easily altered versus the time when it's "off", thusly altering the NET power to the solenoid, motor etc. This is called the duty-cycle, or the mark-space ratio. Why go to all this bother? Very simple. Switching is almost lossless, something around 1% losses would be typical. A big variable resistor might be 50% typical losses, get warm, be expensive and have a big bulk. PWM control is simple for a microprocessor.
Of course, there are drawbacks, are'nt there always? You have to be careful about back EMF. from the coil on the solenoid (it's an inductor). But the microprocessor is cleverly designed. Every so often the micro. tests the coil by putting a pulse to it and then looking for the back EMF. If it finds none, or it's wrong, an errorcode is flagged up. This means not only has the RESISTANCE of the solenoid to be right, the IMPEDANCE* has to be right too. Only one shorted turn in the solenoid coil will reduce the impedance dramatically and therefore the back EMF, but make almost no difference to the resistance. The micro. will detect this during it's regular testing using the operation described above. So if you're going to truly test one of THESE solenoids, a pure dc from an ohm-meter won't do. Now you can see if you had a 12volt solenoid in your hand with a shorted turn fault and you put 12volt across it from a battery, it would click in and out quite smartly. But it would be no good for a PWM 12volt supply, microprocessor checked say every second or so.
Leedsman.
* RESISTANCE is the current-limiting effect of a conductor to smooth dc power, e.g. a tungsten lamp, an electric fire. Low frequency ac (e.g. the mains of 50 or 60Hz) through lamps and fires etc. also works like dc, and the wattage calculations are the same. Hence the term RMS (Root-Mean-Square) which is the effective ac voltage or current as an EQUIVALENT to dc. So 230volt/50Hz has the same power effect in resistors as 230volt dc.
IMPEDANCE is much more complicated. In a pure resistor, resistance and impedance are the same at any frequency; the "pure" resistor is theoretical BTW, non-existent in real-world. But at low frequencies, it's near enough the same.
Impedance is the 'resistance' to ac, and directly proportional to frequency. Higher frequency, more impedance. Example; a bass loudspeaker might have a dc resistance of 6ohm, be called an "8-ohm" speaker, and have an impedance of hundreds of ohms at 10KHz. So a solenoid could have a dc resistance of say, 24ohm and draw half an amp from a 12volt battery (pure dc), but quite a high impedance of hundreds of ohms to a very short "test-pulse" dc from a micro. If it has a shorted turn, or a bad soldered joint/weld, is jammed, that impedance will not be 'in-spec'.
I put this in later, although the contribution is getting a bit long...Often, solenoids have a diode across them to squash back EMF. I would employ one if driving the solenoid in PWM mode. It may be a plain silicon diode, or it might be a zener diode if I were meauring the back EMF as part of the micro's routine testing. Whatever, when they go wrong they go DEAD-SHORT, therefore dead easy to check with an ohm-meter on low scale, i.e. to measure resistance less than 100ohm. If it is deadshort, take it to any electronics hobbyist stores, they can find out from their diode lists exactly what it is. The type # is printed on the plastic body near the polarity ring, probably 1Nxxxx. This is more likely than an o/c coil. Of course measure it both ways round!