2005 S80 Automatic Transmission limp mode

[Hermit]

Hi gentlemen,
My Volvo S80 Automatic Transmission drives like a dream until the Transmission goes into limp mode. It's in Excellent condition throughout and I'm seriously thinking of scrapping it.

The codes were all cleared for me then I went for a short drive and Transmission went into limp mode and below are the codes.

I've spent hours looking at possible causes but it's still doing it.

Central Electronics Module
3F03 Shift Lock Signal Too Low
1A61 Communication With TCM Control Module Missing
3F83 Immobiliser Signal Too Low

Petrol Engine Control a Module
512B Malfunction Indicator Lamp Communication signal Missing

[RickHaleParker]

Strongly indicates a problem with communications not component failure.

CEM-3F03 & CEM-3F83 can both be caused by a communications problem with between the shifter and the CEM. CEM-1A61 is a communications problem between the TCM and the CEM.

I suggest you pull the CEM and clean the contacts. Look for defects in the wiring harness.

[Hermit]

Hi Rick,
I have pulled out the CEM and cleaned every contact even though they were all clean. I also pulled all the fuses and cleaned them as well and again they were all clean. Yes, it appears to be a Comms problem.
I will take out the shifter like you suggested & look for a problem there. This seems to be e fairly common problem with Volvo's. Any other suggestions?
Thank you very much,
Ivan

[RickHaleParker]

CEM-3F03 Shift lock signal. Signal too low

Diagnostic trouble code (DTC) information CEM-3F03

Condition
The central electronic module (CEM) checks the function of the shift lock.
The diagnostic trouble code (DTC) is stored if the central electronic module (CEM) detects a short-circuit to ground or an open-circuit in the output signal circuit to the shift lock.
The relay for shift lock must not be activated for the diagnostic trouble code (DTC) to be stored. The diagnostic trouble code (DTC) can be diagnosed at ignition switch position II.

Substitute value
None.

Possible source
Open-circuit in the “Inhibited shifting” output signal. The relay is not activated.

Fault symptoms
The starter motor does not turn
The engine does not start.

---------------------------------------------

CEM-3F83 Immobilizer signal. Signal too low

Diagnostic trouble code (DTC) information CEM-3F83

M4303790 Condition
The central electronic module (CEM) receives information from the transmission on a hardwired cable indicating when park or neutral are engaged. The central electronic module (CEM) also receives a signal indicating the position of the gear-shift position sensor from the transmission control module (TCM) via the controller area network (CAN).
The diagnostic trouble code (DTC) is stored if the central electronic module (CEM) detects that the gear-shift selector lever is in position P or N but the position received from the transmission control module (TCM) on the controller area network (CAN) indicates a different position.
The diagnostic trouble code (DTC) can be diagnosed in ignition positions II and III.

Substitute value
None.

Possible source
Short-circuit to ground in the cable from the gear-shift position sensor.

Fault symptoms
The park neutral position (PNP) switch does not function.

[RickHaleParker]

CEM-1A61 Communication with the transmission control module (TCM). Signal missing

Diagnostic trouble code (DTC) information CEM-1A61

D4301826 Condition
The diagnostic trouble code (DTC) is stored if the central electronic module (CEM) registers that communication with the transmission control module (TCM) is not operating.
The diagnostic trouble code (DTC) can be diagnosed when the ignition has been on for more than 10 seconds.
Note! If CEM-1A6X diagnostic trouble codes (DTCs) are stored, the central electronic module (CEM) must not be replaced as the diagnostic trouble code (DTC) indicates a communication fault in the Control area network!

Substitute value
None.

Possible source

• No power supply to the transmission control module (TCM)
  Open-circuit in the ground lead to the transmission control module (TCM)
  Contact resistance in the terminals
  Open-circuit in the wiring for the CAN high speed network to the transmission control module (TCM)
  The transmission control module (TCM) is not intended for this vehicle, for example a used control module with different software/hardware.

Hint:
If several diagnostic trouble codes (DTCs) are stored in the central electronic module (CEM) for communication faults with other control modules in the high speed network, this indicates a common fault in the Control area network, see the wiring diagram.

Fault symptoms
No shifting.
Malfunction indicator lamp (MIL) lit
Message in the display.