4T45E DTC P0843 - keywords MIL MN5 pressure release SES slip TCC

This PI was superseded to update model years. Please discard PIP4228.

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

If the above vehicle has a DTC P0843 follow recommendations below.

Use eSI Document ID 1615446 for all models listed above with 4T45E transmission. The circuit/ system verification reads as follows.

1. Drive the vehicle in D4 until the transmission shifts into 4th gear and the TCC is commanded ON. Observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should display No.

•	If the TCC Release Pressure displays Yes, turn OFF the engine and disconnect the AT 20-way inline connector. Using the J 35616, jumper the TCC release switch circuit at the engine harness side to ground. Turn ON the ignition with the engine OFF.

•	If the TCC Release switch parameter displays Yes, test the TCC release switch circuit for an open between the TCM and the AT 20-way inline connector.

•	If the parameter displays NO, test the TCC release switch signal circuit for an open between the AT 20-way inline connector and the TFP manual valve position switch.

2. Reconnect the AT 20-way inline connector. Start the engine and observe the TCC Release Pressure parameter on the scan tool. The TCC Release Pressure should indicate Yes.

If the TCC Release Pressure displays No, disconnect the AT 20-way inline connector.

3. With the AT 20-way inline connector disconnected, observe the TCC Release Pressure parameter on the scan tool. The parameter should display Yes.

•	If the parameter displays Yes, test the TCC release switch signal circuit for a short to ground between the AT 20-way inline connector and the TFP manual valve position switch.

•	If the parameter displays No, test the TCC release switch signal circuit for a short to ground between the TCM and the AT 20-way inline connector.

•	If at this stage the concern is not found previous cases indicate the concern is most likely the TCC o-ring #41.

4. Inspect for the following conditions that would cause TCC release pressure to be present when the TCC is applied:

•	The turbine shaft O-ring seal leaking

•	The turbine shaft oil seal rings missing or damaged--refer to Torque Converter Assembly Removal.

•	The TCC control valve damaged--refer to Control Valve Body Disassemble.

•	The #1 checkball damaged

•	The spacer plate release exhaust blocked with debris--refer to Control Valve Body Assemble.

•	The case cover or spacer plate gaskets improperly installed--refer to Control Valve Body Cover Removal.

•	If any of the conditions are found, repair as necessary.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.