P1798

CODE NUMBER
Scan tool: 73
General scan tool: P1798

CODE NAME
Worn out/burnt transmission fluid

CODE DESCRIPTION
Technical Description
While in 3rd or 4th gear Fully Electronically Modulated Converter Clutch (FEMCC) and just before the A/C clutch engages, the Powertrain Control Module (PCM) requests the Transmission Control Module (TCM) to momentarily establish Partial Electronically Modulated Converter Clutch (PEMCC) operation. If vehicle shudder is detected during the FEMCC to PEMCC transition, a counter is incremented. If the count reaches 20, the trouble code is set. The driver may then notice harsh bumps when the A/C clutch is being cycled, but vehicle shudder will be eliminated. After 35 OBD II warm-up starts or it the code is cleared, PEMCC will be reactivated to see if shudder is still present. If one shudder event occurs, the code will be reset. Clearing the code and battery disconnect is the only way to reset the shudder counter from 20 back to zero.

Check Area
At every PEMCC transition when A/C compressor clutch is being cycled.

Set Conditions
The code will be set if the vehicle shudder is detected 20 times when the A/C clutch is cycled.

Transmission Effects
This code does not cause the transmission to go into limp-in mode. However, once the code is set, FEMCC to PEMCC operation before the A/C clutch engagement will be disabled for 35 OBD II warm up starts.

PROBABLE CAUSE
- Degraded fluid
- Wheels severely out of alignment
- Internal torque converter problem





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