VALVE GP-A/C & HEATER CONTROL 2678562 - Caterpillar

The supply voltage is routed to terminal 1 of each sensor connector. The sensor return is routed to terminal 2 of each sensor connector. The sensor signal is routed to terminal 3 of each sensor connector. The ECM provides short circuit protection for the internal power supply. A short circuit to the battery will not damage the internal power supply.Note: The fuel rail pressure sensor terminal positions are non-standard. The sensor return is routed to terminal 1, the signal to terminal 2, and supply voltage to terminal 3.Reference: Refer to Schematic, Component Location for the locations of the sensors and the sensor connectors.
Table 2
Troubleshooting Test Steps Values Results
1. Check for Codes
A. Establish communication between Cat® Electronic Technician (ET) and the A6:E2 ECM . Refer to Troubleshooting, "Electronic Service Tools", if necessary.
B. Turn the keyswitch to ON.
C. Look for a -3, or -4 active or logged codes:
Codes
Result: A -3 code is active.
Proceed to Test Step 2.
Result: A -4 code is active.
Proceed to Test Step 3.
Result: A 2458-2 or 3251-2 code is active.
Proceed to Test Step 5.
2. Create a Short at the Sensor Connector
A. Use a jumper wire to create a short circuit between the sensor signal and sensor return at the sensor connector.
B. Turn the keyswitch to ON.
C. Monitor the diagnostic codes on Cat ET. Check for an active -4 diagnostic code for the suspect sensor.
D. Turn the keyswitch to OFF.
Short Circuit
Result: A -4 diagnostic code became active after creating the short at the sensor connector. The wiring is OK.
Repair: Replace the sensor. Verify that the problem is resolved.
Result: A -4 diagnostic code does not become active for the suspect sensor.
Repair: Repair the wiring or replace the harness. Verify that the problem is resolved.
3. Create an Open at the Suspect Sensor Connector
A. Turn the keyswitch to OFF.
B. Disconnect the sensor connector of the suspect sensor with the active -4 diagnostic code.
C. Turn the keyswitch to ON.
D. Monitor the diagnostic codes on Cat ET. Check for an active -3 diagnostic code for the suspect sensor.
E. Turn the keyswitch to OFF.
Open Circuit
Result: A -3 diagnostic code became active after disconnecting the sensor. The sensor signal wiring is OK.
Proceed to Test Step 4.
Result: A -3 diagnostic code did not become active after disconnecting the sensor.
Repair: Repair the sensor signal wiring or replace the harness, Verify that the problem is resolved.
4. Check the 5 VDC Supply Voltage at the Sensor Connector
A. Turn the keyswitch to ON.
B. Measure the voltage between the sensor supply and sensor return at the suspect sensor.
Supply Voltage
Result: The supply voltage is approximately 5.0 0.2 VDC
Repair: Replace the sensor. Verify that the problem is resolved.
Result: The supply voltage is not approximately 5.0 0.2 VDC. There is a short circuit in the harness to the ECM.
Repair: Repair the wiring or replace the harness. Verify that the problem is resolved.
5. Inspect the DPF Differential Pressure Lines, Fittings, and Manifold
A. Ensure that the DPF differential pressure lines are connected.
B. Ensure that the DPF differential pressure lines, fittings, and manifold are free