Test Procedure

AT1 PRELIMINARY DIAGNOSIS FOR DTC P2552

Is DTC P2552 present?

Yes	No
For DTCs P1378 or P1379, GO to Pinpoint Test S For DTC P2552, GO to AT2. For DTC P0148, GO to AT5.	CLEAR the DTCs. REPEAT the self-test. For all other DTCs, refer to DIAGNOSTIC TROUBLE CODE (DTC) DESCRIPTIONS .

AT2 DIAGNOSTIC TROUBLE CODE (DTC) P2552

NOTE: Refer to Figure for PCM and component connector pin numbers at the beginning of this pinpoint test.

Possible causes:
- FICMM line open
- FICMM line shorted to ground
Key OFF.
Disconnect the FICM electrical harness connector C.
Key ON, engine OFF.
Measure the voltage between the FICM connector C pin 9, harness side and ground.

Is the voltage greater than 10.5 volts?

Yes	No
CLEAR the DTCs. REPEAT the self-test. If DTC P2552 is present again, INSTALL a new FICM.	GO to AT3.

AT3 CHECK THE FICMM CIRCUIT FOR A SHORT TO GROUND

Key OFF.
Disconnect the PCM engine harness connector.
Measure the resistance between the PCM engine harness connector pin 28, harness side and ground.

Is the resistance greater than 10,000 ohms?

Yes	No
GO to AT4.	REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.

AT4 CHECK THE FICMM CIRCUIT FOR AN OPEN

Measure the resistance between the PCM engine harness connector pin 28, harness side and the FICM connector C pin 9, harness side.

Is the resistance less than 5 ohms?

Yes	No
CLEAR the DTCs. REPEAT the self-test. If DTC P2552 is present again, INSTALL a new PCM.	REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.

AT5 DIAGNOSTIC TROUBLE CODE (DTC) P0148

Possible causes:
- Fuel quality
- Crankshaft position (CKP) or camshaft position (CMP) signal noise
Retrieve and record all engine and transmission DTCs.

Is DTC P0148 present?

Yes	No
REFER to PERFORMANCE DIAGNOSTIC PROCEDURES . CARRY OUT a drive cycle. REFER to DIAGNOSTIC METHODS - EXCURSION (6.0L DIESEL) . REFLASH the PCM. If DTC P0148 is present again, INSTALL a new PCM.	REFER to SYMPTOM CHARTS - 6.0L DIESEL if a driveability concern exists.