Thread: Auto trans limp mode

Thanks will follow your direction slowly and will report back.

Yes is makes it very difficult when you cannot trust rave

Good luck, i'd be inclined to trust the attached doc from many i've seen, this looks the most accurate to me(which doesnt mean it really is ) but at least confirms that across 14 - 42 you should see the sensor's load

I hope you find something electrical, as it would be easier, but there's a fair chance it may be internal.

If you had time, then I'd suggest pulling the valve body and going through that, also cleaning any friction material from the screen for the TC lock up solenoid as the circuit affects line pressures also.

while the valve body is off, blow compressed air ( about 20-30 psi ) through the 7 galleries with the rubber grommets ( behind the springs and circlips ) as this will tell you if you have a major leak through an O ring etc

However, if you pull the pan and find glitter, it'll be a complete overhaul, unfortunately.

best of luck

One other thing I was thinking(how I'm reading it) is that if the harness is damaged in some way(crushing/rubbing through) it should have worn through the shielding first.

Like SF says, at pins 42/14 of the TCU connector you should have a reading(300 ohms or something), but you should have nothing between pin 15(the shielding core), which is a white wire, and pins 42 or 14. If you have continuity between pins 42 and/or 14 and pin15 in the harness, then for sure wire damage.

But be careful with the white wire and pin 15, which isn't shown in the wiring diagram, pin 16 is also white but this one goes to the ECU.

Ive parked it up for a bit as ive now got to do a timing belt kit on an old Audi 80 v6 which if you know is the whole front has to come off to get access.

I am getting the reading for pin 14 to 42 which to me means the speed sensor circuit is good but what throws me is open circuit between the trans connector pin E and F to pins 14 and 42

I have removed the trans loom stripped and checked for breaks etc and all good.

If it is internal failure id still be getting circuit readings and stall a test shows 2700rpm at normal operating temp. Car has only traveled 160k klm

I have always shied away from electrics I find it a dark magic and keeps me awake at night


But thank you to all I will systematically go through all suggested checks and report back

Originally Posted by thai_tiger

.....
I am getting the reading for pin 14 to 42 which to me means the speed sensor circuit is good but what throws me is open circuit between the trans connector pin E and F to pins 14 and 42

.....

and just to be sure, E->42 and F->14 is where you should have continuity.
I'm sure you checked this, as you've already stated you have earlier, but for a laugh, check the other way around too, just in case.
Possible that you inadvertently did check E->14 and F->42 which WILL have open circuit. Pins E and F are very close together and easy to mistake them.
You wouldn't be the first to chase your tail doing something along the lines of this

if you still have open circuit on the correct line configs, make no sense that you have continuity(and about 300-ish ohms) then between 14 and 42 at the TCU end of the loom(if you have checked the resistance measurement, not just continuity), and the intermediate 678/728 pin 1/2 connection.

So if it does turn out that you have open lines for the E->42 and F->14 lines, keep trying and maybe wriggle the wires about a bit. Could be an intermittent connection, that works when you have pressure on the wires/loom one way, but then not work if you have them another way.

Originally Posted by AK83

I'm sure you checked this, as you've already stated you have earlier, but for a laugh, check the other way around too, just in case.

Back in my RAEME days had a mate whose nickname was Diode, precisely for doing this....

Originally Posted by thai_tiger

I am getting the reading for pin 14 to 42 which to me means the speed sensor circuit is good but what throws me is open circuit between the trans connector pin E and F to pins 14 and 42

Very strange cos the red part excludes the blue or vice-versa so in this case i can think that you are missing something there as what you say is technically impossible, the blue text contradicts the big red part cos if in reality one(or both) of E -> 42 or F -> 14 is open circuit then the sensor circuit is not good if you see what i mean

though IF the circuit is actually good and so is the sensor while the mechanical stall test passed you should replace the TCU to rule it out