P144E

P144E-EGR COOLER BYPASS STATUS LINE CIRCUIT LOW





For a complete wiring diagram, refer to the Wiring Information.

Theory of Operation

The Exhaust Gas Recirculation (EGR) Cooler Bypass Valve is used to redirect the EGR gases around the cooler when the engine is under certain operating conditions. The EGR Cooler Bypass Valve is a smart device which communicates it's status to the Powertrain Control Module (PCM). At key on the EGR Cooler Bypass Valve drives the signal line low and then high and the PCM monitors for the correct status response from the EGR Cooler Bypass Valve. Throughout engine operation the PCM sends commands via the signal circuit to the EGR Cooler Bypass Valve and monitors the status line to confirm that the EGR Cooler Bypass Valve has reached the commanded position. When a fault occurs, the EGR Cooler Bypass valve will send a signal of less than one Volt on the status line to the PCM. This monitor is a one trip fault. The valve will continue to operate properly if it is not the cause of the fault. This fault may also be accompanied with a P245C.

- When Monitored:
Continuously with key on.

- Set Condition:
The voltage detected at the PCM for the EGR Bypass Status line is below a calibrated threshold for a calibrated amount of time.





Always perform the Pre-Diagnostic Troubleshooting procedure before proceeding. Pre-Diagnostic Troubleshooting Procedure.

1. ACTIVE DTC
1. Turn the ignition on.
2. With the scan tool, record all Freeze frame data.
3. With the scan tool, erase DTCs.
4. Turn the ignition off for 75 seconds.
5. Turn the ignition on.
6. With the scan tool, read DTCs.

Did the DTC return?

Yes

- Go To 2

No

- Perform the INTERMITTENT CONDITION - 6.7L diagnostic procedure. Intermittent Condition Test

2. OTHER DTCs
1. Ignition on, engine not running.
2. With the scan tool, read DTCs.

Are faults also present for the VGT and Mass Airflow Sensor?

Yes

- Repair the (F344) Smart Power Relay Coil circuit for an open or short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 3

3. CHECK THE EGR COOLER BYPASS POWER AND GROUND
1. Turn the ignition off.
2. Disconnect the EGR Cooler Bypass Valve harness connector.

NOTE: Check connectors - Clean/repair as necessary.

3. Turn the ignition on, engine not running.
4. Measure the voltage between the (F344) Smart Power Relay Coil circuit and the (Z902) Ground circuit at the EGR Cooler Bypass Valve harness connector.

Is the voltage equal to battery voltage?

Yes

- Go To 5

No

- Go To 4

4. CHECK THE (Z902) GROUND CIRCUIT
1. Turn the ignition off.
2. Measure the resistance between ground and the (Z902) Ground circuit at the EGR Cooler Bypass Valve harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Repair the (F344) Smart Power Relay Coil Feed circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Repair the (Z902) Ground circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

5. CHECK THE (K671) EGR COOLER BYPASS VALVE STATUS LINE FOR A SHORT TO GROUND
1. Turn the ignition off.
2. Disconnect the PCM C1 harness connector.

NOTE: Check connectors - Clean/repair as necessary.

3. Measure the resistance between ground and the (K671) EGR Cooler Bypass Valve Status Line circuit at the EGR Cooler Bypass Valve harness connector.

Is the resistance below 10k Ohms?

Yes

- Repair the (K671) EGR Cooler Bypass Valve Status Line circuit for a short to ground.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 6

6. CHECK THE (K671) EGR COOLER BYPASS VALVE STATUS LINE FOR AN OPEN/HIGH RESISTANCE
1. Measure the resistance of the (K671) EGR Cooler Bypass Valve Status Line circuit between the EGR Cooler Bypass Valve harness connector and the PCM C1 harness connector.

Is the resistance below 5.0 Ohms?

Yes

- Go To 7

No

- Repair the (K671) EGR Cooler Bypass Valve Status Line circuit for an open or high resistance.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

7. CHECK THE EGR COOLER BYPASS VALVE




1. Reconnect the PCM C1 harness connector.
2. Leave the ignition in the off position for a minimum of 10 minutes to allow the PCM to completely power down.
3. Use a jumper wire to connect 12-Volts to the (K671) EGR Cooler Bypass Valve Status Line circuit.
4. Turn the ignition on.
5. With the scan tool, read DTCs.

Is P144F present?

Yes

- Replace the EGR Cooler Bypass Valve.
NOTE: After inducing the P144F fault, the PCM must be powered down for 10 minutes in able to clear the DTC.

- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Replace Powertrain Control Module.
- Replace and program the Powertrain Control Module. PCM/ECM Reprogramming