Synchro Reverse Gear Not Engageable Or Gear Skip

P177B

Diagnosis information - PDK

Synchro reverse gear not engageable or gear skip

Diagnostic conditions
The control unit initially tests internal function sequences when the ignition is switched on (terminal 15). If they are OK, all diagnosable outputs are then tested and any faults are stored.

- Ignition on
- The following faults are not detected: P1731, P1732, P1733 or P1734
- The following faults are not detected: P1706 or P1707
- Alternative measure HSS3_OFF not active

Possible fault causes
- Hydraulics faulty (hydraulic control unit)
- Transmission faulty

Fault setting conditions
- Target gear Reverse gear, actual gear is disengaged before pressure adjusters 5/6 are activated
- 2nd gear is engaged instead of reverse gear
- No shift rod moves

NOTE: The individual detection times are temperature-dependent (cold 2 s, warm 1 s)

Fault effects
- Gear held
- Only gears 1, 2, 4 and 7 are possible
- Transmission limp-home indication in instrument cluster control unit