P38A 2001 4.0 Gearbox Fault

PastyMuncher83 · Mar 24, 2018

Another week another dash bong! This time it’s flashing gearbox Fault and stuck in third gear/limp mode.

Have checked in here and tried the easy things. Fitted a brand new battery although my old one was testing fine.

Took out the full plug to check level and all fine. If anything was over filled as about 1/4 litre came out the fill plug and was clear red.

Disconnected and sprayed with contact cleaner all the electrical plugs on the gear box.

Have just ordered a 2nd hand Trans ECU in the hope that’s the culprit. No obvious signs of damage/moisture on the existing ecu.

Gearbox was working perfectly before the Fault beep came up.

My Hawkeye can’t clear the Fault codes but see attached images for stored faults, seems Canbus related?!

Any help greatfully appreciated as ever

Orangebean · Mar 24, 2018

Your autobox fluid level check wasn't quite correct. See Refill, and with oil cold:

PastyMuncher83 · Mar 26, 2018

Ok so have a second hand transmission ECU on the way and have ordered the parts to do a filter change and will replace the fluid with the method above and see if that solves it on the weekend.

When cycling through the gears with the engine idling for refill level, will all four wheels have to be off the floor/able to rotate or can I get away with just holding it on the footbrake with wheels on the floor?

Orangebean · Mar 26, 2018

On the floor with the parking brake on, in Park and footbrake on is fine. You don't have to cycle through gears while filling.

PastyMuncher83 · Mar 30, 2018

Fluid and filter replaced.
Transmission ecu replaced with 2nd hand item.
Battery Replaced.
Earths checked and positive in fuse box and on starter all checked.

Still displays gearbox Fault and showing the same codes as above.

Any other suggestions or has the death bong finally rung for my P38?

Saint.V8 · Mar 30, 2018

Has it been on diagnostics and had the faults cleared?

PastyMuncher83 · Mar 30, 2018

Yeah although now I can’t clear the transmission codes with my Hawkeye, after trying comes up with faults not cleared.
They did clear but after about a mile drive they come back up.

Always the same transmission codes-

P1841
P1842
P1843

Checked the EMS codes which I can clear and stores the following.

Fault 108

Continuous Power Supply Interruption Minimum Value not reached. Fault NOT present and static.

Fault 236 P0600

Can timeout EGS/Auto transmission CM signal missing. Fault present and intermittent.

Saint.V8 · Mar 30, 2018

Check the attached PDF - page 7 I think.....it isn't or doesn't appear to be a gearbox mechanical fault - looks to be a problem on the CAN possibly and Engine ECU or Gearbox ECU issue..... follow some of the guidance in the document and see wher eit leads!

PastyMuncher83 · Mar 31, 2018

Thanks for your Input Saint,

Will read up on that guidance.

Seems I definetly have a P38 gremlin, shame after so many years of P38’s but I guess eventually luck runs out.

Maybe spending at the Volvo dealership sooner than I had hoped!!

PastyMuncher83 · Mar 31, 2018

I’m gonna try and take the transmission wiring harness out and check every wire for continuity.

Failing that will have to fit another engine ecu and see if that works.

PastyMuncher83 · Apr 10, 2018

After dousing the loom with wd40, and a week in the workshop drying out whilst waiting for a heater return hose pipe to arrive to cure the coolant leak, have done 300 odd miles now and box is working fine with no more codes

Seems the coolant leak, which was right on the underneath of the expansion tank return hard pipe, had got moisture onto the gearbox loom.

P38A 2001 4.0 Gearbox Fault

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