P144F

P144F-EGR COOLER BYPASS STATUS LINE CIRCUIT HIGH





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.

- When Monitored:
With the ignition on.

- Set Condition:
The PCM has detected battery voltage on the status line when no voltage should be present.





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

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

Is DTC P144F active?

Yes

- Go To 2

No

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

2. CHECK THE (K671) EGR COOLER BYPASS STATUS CIRCUIT FOR A SHORT TO BATTERY VOLTAGE
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.
4. Measure the voltage at the (K671) EGR Cooler Bypass Valve Status Line circuit at the EGR Cooler Bypass Valve harness connector.

Is the voltage equal to battery voltage?

Yes

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

No

- Go To 3

3. CHECK THE SMART POWER RELAY
1. Turn the ignition off.
2. Measure for voltage at the (F344) Smart Power Relay Coil circuit at the EGR Cooler Bypass Valve harness connector.

Is there any voltage present?

Yes

- The Smart Power Relay is stuck on. If there are any Smart Power Relay Control circuit DTCs present, diagnose those before replacing the Smart Power Relay.
- Perform the POWERTRAIN VERIFICATION TEST - 6.7L. Powertrain Verification Test.

No

- Go To 4

4. CHECK THE EGR COOLER BYPASS VALVE




1. Turn the ignition to the off position for a minimum of 10 minutes to allow the PCM to completely power down.
2. Use a jumper wire to connect the (K671) EGR Cooler Bypass Status circuit to ground.
3. Turn the ignition on.
4. With the scan tool, read DTCs.

Did P144F go inactive?

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 and program the Powertrain Control Module. PCM/ECM Reprogramming