The Electronic Control Module (ECM) provides 12.7 ± 1.0 VDC from ECM connector P1-51 to pin A at the sensor connectors. The sensor's return line is pin B of the sensor connectors. Pin B is connected to the digital return line P1-9 of the ECM.
The engine has the following digital sensors: throttle position sensor, brake oil temperature sensor and engine fan speed sensor.
The digital sensor supply is output short circuit protected. A short circuit to the battery should not cause permanent damage to the circuit inside the ECM. The digital sensors are not protected from overvoltage.
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| Illustration 1 | g00935613 |
Test Step 1. Check for Connector Damage.
- Turn the keyswitch to the OFF position.
- Thoroughly inspect the ECM connector J1/P1 and the machine connector J2/P2. Inspect all of the other connectors. Refer to the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors" for details.
- Perform a 45 N (10 lb) pull test on each of the wires in the ECM connector that are associated with the circuit.
- Check the ECM connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).
- Check the machine connector (allen head screw) for the proper torque of 2.25 ± 0.25 N·m (20 ± 2 lb in).
- Check the harness and the wiring for abrasion and for pinch points.
Expected Result:
The connectors and wiringare free of the following problems: damage, corrosion, abrasion and incorrect attachment.
Results:
- OK - The connectors and wiring are okay. Proceed to Test Step 2.
- Not OK - The connectors and/or wiring need repair.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring.
Stop.
Test Step 2. Check the Digital Supply Voltage at the ECM.
- Remove the digital supply line on wire A700-OR on pin P1-51 of the ECM. Install a jumper into the socket P1-51.
- Remove the digital return line 998-BR on pin P1-9 of the ECM. Install a jumper into the socket P1-9.
Note: The digital return will no longer be connected to the other sensors and switches. Additional diagnostic codes will be generated from the ECM. Clear the codes after you complete this test.
- Reconnect the ECM connector.
- Turn the keyswitch to the ON position. The engine should be off.
- Measure the voltage between the wire jumpers in P1-51 and P1-9.
- Turn the keyswitch to the OFF position.
- Remove the jumpers and replace all wires.
Expected Result:
The supply voltage is 12.7 ± 1.0 VDC.
Results:
- OK - The supply voltage is 12.7 ± 1.0 VDC. The digital sensor supply is producing the correct voltage. Proceed to Test Step 3.
- Not OK - The supply voltage is not 12.7 ± 1.0 VDC. The digital sensor is not producing the correct voltage.
Repair: Perform the diagnostic functional test Troubleshooting, "Electrical Power Supply".
Stop.
Test Step 3. Check the Digital Sensor Supply Voltage at the Sensor Connector.
- Turn the keyswitch to the ON position. The engine should be off.
- Measure the digital sensor supply voltage between terminal-A and the digital return terminal-B of all the digital sensors.
Expected Result:
The supply voltage is 12.7 ± 1.0 VDC.
Results:
- OK - The supply voltage is 12.7 ± 1.0 VDC. The supply voltage is present at all of the digital sensor connectors. Proceed to Test Step 6.
- Not OK - The supply voltage is not 12.7 ± 1.0 VDC. The supply voltage is not correct. There is an open circuit in the harness or in the connectors. Proceed to Test Step 4.
Test Step 4. Check for a Short Circuit in the Wiring Harness.
- Disconnect ECM connector J1/P1 and all of the digital sensors.
- Measure the resistance between the digital supply wire A700-OR at the ECM connector P1-51 and the digital return wire 998-BR on the ECM connector P1-9.
- Measure the resistance between the digital supply wire A700-OR at the ECM connector P1-51 and the engine ground.
- Measure the resistance between the digital return wire 998-BR at the ECM connector P1-9 and the engine ground.
- Reconnect all connectors.
Expected Result:
The resistance is greater than 20,000 Ohms for each measurement.
Results:
- OK - The resistance is greater than 20,000 Ohms. Proceed to Test Step 5.
- Not OK - The resistance is less than 20,000 Ohms. There is a short in the harness.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify repair by rechecking for shorts in the harness.
Stop.
Test Step 5. Check for an Open Circuit in the Wiring Harness.
- Disconnect ECM connector J1/P1 and all of the digital sensors.
- Install a wire jumper between wire A700-OR at the ECM connector P1-51 and the digital return wire 998-BR on the ECM connector P1-9.
- Measure the resistance between terminal-A and the digital return terminal-B of all the digital sensors.
- Remove the wire jumper and reconnect all connectors.
Expected Result:
The resistance is less than 5 Ohms.
Results:
- OK - The resistance is less than 5 Ohms. Proceed to Test Step 6.
- Not OK - The resistance is not less than 5 Ohms. There is an open in the harness.
Repair: Repair the connectors or wiring and/or replace the connectors or wiring. Verify repair by rechecking for opens in the harness.
Stop.
Test Step 6. Check the Digital Sensors for Short Circuits.
- Disconnect all digital sensors.
- Turn the keyswitch to the ON position. The engine should be off.
- Connect one digital sensor at a time.
- Check the digital sensor supply voltage between the digital supply terminal-A (A700-OR) and the digital return terminal-B (998-BR). Repeat this step with all of the digital sensors.
- Turn the keyswitch to the OFF position.
- Reconnect all digital sensors.
Expected Result:
The supply voltage is 12.7 ± 1.0 VDC.
Results:
- OK - The supply voltage is 12.7 ± 1.0 VDC. The digital sensor supply and the harness are okay.
Repair: The problem may be intermittent. Perform the diagnostic functional test Troubleshooting, "Inspecting Electrical Connectors".
Stop.
- Not OK - The supply voltage is not 12.7 ± 1.0 VDC. The supply voltage is not correct. The sensor may be internally shorted.
Repair: Temporarily connect a new sensor. Verify that the new sensor solves the problem before permanently installing the new sensor.
Stop.