Help with Limp Mode, ECM communication issues

[sangeeth911]

Car is a 2002.5 S-Type - VIN M59756 / 2.5 V6~ ZF6HP

Driving around a few weeks back, gearbox fault message appears and amber warning light comes on, goes into limp home mode (no other MILs or warnings); but a strange whiny noise from the gearbox (I'm guessing because of the limp home activation).

Here are all the things I tried:

Battery fully charged, left overnight, holds 12.6 volts steady even after 30 sec accessories test.

Disconnected battery, touched cables together for 20 seconds, left overnight, start-up in the morning, same (gearbox fault) message comes up immediately.

Since I've got the IDS/Mongoose, quick scan revealed the following:

ECM: [ERR0xc] Communications with the module have been lost

General Electronics control module: U1041 Vehicle speed not obtained

Rear Electronics control Module: U1041 Vehicle speed not obtained (further description) ABS/ Dynamic stability control wheel speed message error. SCP network error.

Transmission control module: P0715 Input / turbine speed sensor circuit malfunction.

My first thought after seeing the codes was "ABS sensor", but that still doesn't explain the ECM /communication error.

I must add that apart from the limp home, all functions /features / lights/ remotes on the car work perfectly, the car starts, drives flawlessly etc.

Appreciate your expert insight before I throw parts at it.

Sincerely
 

[Mark Five]

My first port of call would be to consider replacing the battery, even though it's holding 12.6v.

Next I'd check the transmission fluid level - I had a similar problem a few years back and the transmission only had a third of the required level, and topping up cured the 'gearbox fault' issue (it was a warped sump, which was plastic and had been over-tightened).

The fault codes might also be historic, and not necessarily relate to your current problem, so I'd clear them and see if they came back later, which they will if there are other faults present.

Good luck!

[garbage-overlord]

The battery ideally needs to hold 12.6 volts for over 24 hours. If it tails off down to 12.5 or 12.4 then it's failing, and needs replacement. Remember that a reading of 12.4v actually means the battery is only at 75% capacity.

[sangeeth911]

19 hours ago, Mark Five said:

My first port of call would be to consider replacing the battery, even though it's holding 12.6v.

Next I'd check the transmission fluid level - I had a similar problem a few years back and the transmission only had a third of the required level, and topping up cured the 'gearbox fault' issue (it was a warped sump, which was plastic and had been over-tightened).

The fault codes might also be historic, and not necessarily relate to your current problem, so I'd clear them and see if they came back later, which they will if there are other faults present.

Good luck!

Thank you for the reply Mark. Yes, I will be replacing the battery today. Over the course of this weekend I've planned to get the car up on jack stands and check the fluid levels and the state of the connector sleeve. 

RE the fault codes:

With the battery disconnected, I removed the rear wheels and cleaned both sensors (cleaned with electronic cleaner, applied dielectric grease to connectors etc) and the reluctor rings (wire brushed all the grease and dirt off after spraying with some de-greaser, noted no damage to any of the cogs). Reconnected the battery, managed to clear the U1041 codes (instead of clicking on the sub-menu or error description, clicking on the main module description brought up the "clear code eraser thingy", drove the car for two ignition cycles (the transmission was in limp mode - 2nd gear the whole time). Rechecked and now the only faults now remaining are the ECM ERR0xC (lost communication) and the P0715 Input speed sensor from the TCM. When using one of the live data logging modes, the TCM value simply shows "no communication".

I've checked pretty much everything else using IDS such as the transmission range sensor (which works fine), brake pedal switch works fine. However, I did notice a weird issue (although I'm not sure whether this is relevant to the current issues or not) - I can move the gear lever out of park and into any gear without depressing the brake pedal (regardless of whether key-in or out, or key position) . The car does detect when the selector is being moved out of park with the ignition on by making that beeping noise. Again - not sure whether this is at all relevant to the P0715 and the ECM communications issue.

Here are some photos off of the IDS screen (taken after Mongoose was disconnected which is why the battery indic shows red).

It seems that the P0715 is the main issue here. I may have jumped the gun by posting without going through with clearing the rest of the code so that one's on me, ergo I still cannot understand the ECM error.

Lastly, I must reiterate that the P0715 comes back instantaneously: even when I clear the code, cycling the ignition to on simply to complete the code erase procedure, brings the fault back up. So perhaps we may be right in inferring that this is an electrical issue and not a mechanical one?
 

[sangeeth911]

19 hours ago, garbage-overlord said:

The battery ideally needs to hold 12.6 volts for over 24 hours. If it tails off down to 12.5 or 12.4 then it's failing, and needs replacement. Remember that a reading of 12.4v actually means the battery is only at 75% capacity.

Yes, that's the first thing on the agenda for today, though I doubt this will cure the limp home mode, I'm hoping it will at least allow for communication with the ECM to be established. 

[JOE-DOT-COM]

hi

P0715 is faulty speed sensor inside gearbox, unless thats cleared, thats the fault

cheers

Joe

[Jimbov8]

Here is a battery charge chart for those who need to know.

[sangeeth911]

2 hours ago, JOE-DOT-COM said:

hi

P0715 is faulty speed sensor inside gearbox, unless thats cleared, thats the fault

cheers

Joe

Thanks for the reply and the information Joe. Kindly point me towards any resources that would help me in achieving this.
Is the speed sensor a part that I can buy separately? Is there a thread on the forum that covers replacement of the speed sensor? I've tried going through the workshop manual and there are no mentions of speed sensor replacement or similar. 

Thanks again!

[sangeeth911]

1 hour ago, Jimbov8 said:

Here is a battery charge chart for those who need to know.

Saved for all future reference! Thank you!

[JOE-DOT-COM]

8 hours ago, sangeeth911 said:

Thanks for the reply and the information Joe. Kindly point me towards any resources that would help me in achieving this.
Is the speed sensor a part that I can buy separately? Is there a thread on the forum that covers replacement of the speed sensor? I've tried going through the workshop manual and there are no mentions of speed sensor replacement or similar. 

Thanks again!

HI

The speed sensor is inside the gearbox on the valve body

the gear box valve body would need removing, I not sure if the speed sensor is replaceable

best option would to speak to a reputable auto gearbox company and ask

cheers

Joe