Symptoms
Symptoms of a P2770 trouble code may include:
- Malfunction Indicator Lamp (MIL) is illuminated (also called check engine light)
- Minimal decrease in fuel economy, this will not affect engine performance
Potential Causes
Causes of this DTC may include:
- Damaged transmission wiring harness, loose connection, open or shorted circuit
- Torque Converter Clutch (TCC) solenoid
- Transmission Control Module (TCM)
Diagnostic Steps for P2770 DTC
Wiring Harness – Check that the transmission wiring harness is not damaged or loose. Use a factory wiring diagram to locate the appropriate power source and all connection points between circuits. The transmission may be powered by a fuse or relay and triggered by the TCM. Disconnect the transmission harness at the transmission connector, power source, and TCM. Check continuity within the internal transmission wiring harness by locating the appropriate + and – pins for the torque converter clutch solenoid.
Using a digital volt ohm meter (DVOM) set to the ohms scale, check the resistance in the circuit with the positive and negative leads on the appropriate pins. If the resistance is extremely high or above the limit (OL), suspect an internal harness or TCC solenoid failure – removal of the transmission oil pan may be necessary to further diagnose the TCC solenoid.
Test the wiring between the TCM and the transmission case wiring harness connector using the DVOM set to ohms. Check for possible short to ground by moving the negative DVOM lead to a known good ground, the resistance should be very high or above (OL).
Torque Converter Clutch (TCC) Solenoid – Check the resistance of the TCC solenoid and internal transmission wiring to the transmission case after removing the transmission harness plug (if applicable, some makes/models use a TCM bolted directly to the transmission case). Some makes/models use a transmission wiring harness with the TCC solenoid and internal harness as a single unit. The DVOM should be set to the ohms scale with the positive and negative leads on the TCC power and control circuit pins. The resistance should be within manufacturer specifications, if it is very high or above the limit (OL), remove the transmission oil pan to inspect the solenoid inside the transmission if possible. Check voltage on the TCC solenoid power circuit or at the wiring harness connector to the TCM with the DVOM set to the volts scale, positive lead to the tested wire and negative to a known good ground with the vehicle key on/engine off, battery voltage should be present.
Transmission Control Module (TCM) – Since the torque converter clutch is only engaged under certain driving conditions, it will be necessary to monitor the TCM with an advanced scan tool to determine if the TCM is commanding the TCC solenoid and what the actual feedback reading is to the TCM. The TCC solenoid is normally controlled by a duty cycle to provide a more comfortable torque converter lockup engagement.
To test if the TCM is actually sending the signal, a graphing multimeter set to duty cycle or a digital storage oscilloscope will also be needed. The positive lead is probed into the wiring harness plugged into the TCM and the negative lead to a known good ground. The duty cycle should match what is commanded by the TCM in the advanced scan tool reading. If the cycle remains at 0% or 100% or is intermittent, recheck connections and if all wiring/solenoid is OK, the TCM may be faulty.