Intermittent No Crank, Starter Clicks, or Vehicle Starts to Crank then Stops Cranking - keywords 3.5 3.9 5.3 crank driveability DTC DTCs electrical engine impala ims intermittent internal LS4 LZ4 LZ8

This PI was superceded to update model years. Please Discard PIC4255.

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

Intermittent No Crank, Starter Clicks, or Vehicle Starts to Crank Then Stops Cranking. Typically there are no DTCs.

The Engine Control Module (ECM) has a separate park / neutral input from the internal mode switch (IMS) on circuit 1786. When the vehicle is in park or neutral, circuit 1786 is pulled low.

Circuit 1786 is routed through the 20 way transmission connector. If there is an intermittent open in circuit 1786, the ECM will not enable the starter relay or if the vehicle is already cranking, the relay will be disabled.

Inspect the 20-way transmission connector for being fully seated. There have been some cases where the connector was not fully seated causing an intermittent open in circuit 1786.

Note:  The schematic for the starter is 1657947 and the schematic for the IMS is 1658032.

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.