Chart C-1 ECM Replacement Check

Chart C-1:

ECM Connector View:

DESCRIPTION:

Prior to replacing an ECM, the vehicle must be tested for:

1. Poor connector terminal to ECM contact.
2. Direct short to battery voltage on an ECM ground circuit.
3. Shorted solenoids or relays. If a short is found, the circuit must be repaired prior to replacing the ECM to prevent repeat ECM failures.

NOTES ON FAULT TREE:

1. Check for poor terminal contact due to weak or dirty ECM terminals. Remove suspected terminals to inspect, replace if broken or dirty. If coolant is present at the ECM connector, replace coolant sensor, coolant sensor connector, and the coolant sensor signal and ground wires. Also, replace ECM connector terminal and blow coolant out of harness. Clean ECM connector with alcohol or spray contact cleaner and replace ECM.

2. Checking for a short to ignition or shorted solenoid or relay. All terminals must be tested since several are connected together internally in the ECM. A short in one circuit may cause another circuit in the ECM to be inoperative. An example might be that the VCC solenoid shorted can cause both VCC to be inoperative and the EGR to be enabled at all times. Any circuit testing below 20 ohms is shorted and should be diagnosed for the cause of the short.

3. Check ISC circuit (EXTEND/RETRACT) for shorted to ground or shorted together. Normal resistance for an ISC motor circuit is 4-100 ohms.