Transmission problem, codes PO743 and PO753

Good morning.

Below are the descriptions and possible causes for the failures. In most cases, it is a wiring issue.

Roy

743

SYMPTOM
P0743-TORQUE CONVERTER CLUTCH SOLENOID/TRANS RELAY CIRCUITS

WHEN MONITORED
Continuously with the key on.

SET CONDITION
This code will set if the voltage detected on the Torque Converter Clutch Solenoid Control circuit at the PCM is different than the expected voltage.

POSSIBLE CAUSES
- TCC solenoid control circuit open
- Fused B+ circuit open
- TCC solenoid control circuit short to ground
- Transmission relay output circuit short to ground
- TCC solenoid control circuit short to voltage
- TCC solenoid control circuit short to other circuits
- Transmission control relay output circuit open
- Torque converter clutch solenoid
- Transmission control relay - poor contacts
- Powertrain control module
- Intermittent wiring and connectors

753

SYMPTOM
P0753-TRANS 3-4 SHIFT SOL/TRANS RELAY CIRCUITS

WHEN MONITORED
Continuously with the key on

SET CONDITION
This code will set if the voltage detected on the 3-4 Shift Solenoid Control circuit at the PCM is different than the expected voltage.

POSSIBLE CAUSES
- P1765 DTC present
- 3-4 shift solenoid control circuit open
- Fused B+ circuit open
- Transmission control relay output circuit open
- 3-4 shift solenoid control circuit short to ground
- Transmission relay output circuit short to ground
- 3-4 shift solenoid control circuit short to voltage
- 3-4 shift solenoid control circuit short to other circuits
- 3-4 shift solenoid
- Transmission control relay - poor contacts
- Powertrain control module
- Intermittent wiring and connectors

That is the last thing I would suspect as well as the valve body.

You need to verify wiring to the transmission. It could be a short in a feed wire or the return to the PCM. All this needs to be checked before throwing a expensive PCM at this that will not resolve the issue.

Make sure there is not transmission fluid in the connector that goes to the transmission.

Roy

Did you pin out the harness and verify voltages to each solenoid?

Roy

Okay, thank you.