818124A 1 Force PISTON .030 OVERSIZE (NOT SHOWN)

Illustration 1 g00952703
SchematicTest Step 1. Inspect Electrical Connectors and Wiring.
Turn the keyswitch to the OFF/RESET position.
Thoroughly inspect the ECM connector J1/P1, the ECM connector J2/P2 and all other connectors in the wiring harness. Refer to Troubleshooting, "Electrical Connectors - Inspect" for details.Expected Result:All connectors, pins, and sockets should be completely inserted and coupled. The harness and wiring should be free of corrosion, abrasion, and pinch points. All connections and grounds should be tight and free of corrosion.Results:
OK - Proceed to Test Step 2.
Not OK - Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.Test Step 2. Check for Shorts in the Harness.
Illustration 2 g00952705
ECM connector
Disconnect the ECM connector J1/P1. Disconnect the ECM connector J2/P2 and all of the analog sensors.
Measure the resistance between P2:2 (Analog Sensor +5V) and P2:3 (Analog Sensor Return).
Measure the resistance between P2:2 (Analog Sensor +5V) and engine ground.Expected Result:The resistance should be greater than 20,000 Ohms.Results:
OK - Proceed to Test Step 3.
Not OK - There is a short between the ECM and the analog sensors.Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.Test Step 3. Check the Analog Sensor Supply Voltage at the Sensor Connectors.
Reconnect the ECM connector J1/P1. Reconnect the ECM connector J2/P2.
Turn the keyswitch to the ON position.
Measure the voltage across terminal A (+5V Analog) and terminal B (Analog Return) at the harness side of each sensor connector.Expected Result:The analog sensor supply voltage should be 5.0 0.5 VDC at each sensor connector.Results:
OK - The supply voltage is reaching the sensors. Proceed to Test Step 4.
Not OK - The supply voltage is not reaching the sensors. Proceed to Test Step 5.Test Step 4. Check the Analog Sensors for Internal Shorts.
Turn the keyswitch to the OFF/RESET position and install a 140-2266 Adapter Cable (70 Pin Breakout T) at ECM connector J1/P1. Install a 140-2266 Adapter Cable (70 Pin Breakout T) at ECM connector J2/P2.
Disconnect all of the analog sensors.
Turn the keyswitch to the ON position.
Measure the voltage across P2:2 (Analog Sensor +5V) and P2:3 (Analog Sensor Return) at the breakout.
Connect each analog sensor individually, while you monitor the supply voltage across P2:2 (Analog Sensor +5V) and P2:3 (Analog Sensor Return) at the breakout.Expected Result:The analog sensor supply voltage should be 5.0 0.5 VDC. The voltage should not drop when the sensors are connected.Results:
OK - None of the analog sensors are internally shorted and there is not a problem with the analog sensor supply circuit.Repair: Refer to Troubleshooting, "Electrical Connectors - Inspect" if the problem is intermittent. Stop.
Not OK - The sensor that pulls down the supply voltage appears to be internally shorted.Repair: Temporarily connect a new sensor.Verify that the replacement sensor solves the problem before you permanently install the new sensor. Stop.Test Step 5. Check the Analog Sensor Supply Voltage at the ECM.
Illustration 3 g00952705
ECM connector
Turn the keyswitch to the OFF/RESET position and install a 140-2266 Adapter Cable (70 Pin Breakout T) at ECM connector J2/P2.
Turn the keyswitch to the ON position.
Measure the voltage across P2:2 (Analog Sensor +5V) and P2:3 (Analog Sensor Return) at the breakout.Expected Result:The supply voltage should be 5.0 0.5 VDC.Results:
OK - The ECM is supplying the correct voltage, but there is an open in the harness between the ECM and the analog sensors.Repair: Repair the circuit.Verify that the repair eliminates the problem. Stop.
Not OK - The ECM is not supplying the correct voltage.Repair: Verify your results.Replace the ECM. Refer to Troubleshooting, "Replacing the ECM" before replacing the ECM.Verify that the repair eliminates the problem. Stop.