Glow Plug Lamp (GPL)

1997 PCED OBDII-Diesel

SECTION 5C: Pinpoint Tests

R: Glow Plug Lamp (GPL)

R: Introduction

R1 DIAGNOSTIC TROUBLE CODE (DTC) P0381

DTC P0381 is set when the PCM detects a malfunction in the glow plug warning lamp circuit.
Possible causes:

Open/grounded circuit
Open WAIT TO START light
Open fuse (F-Series — Fuse 17, Econoline — Fuse 18)

Start engine.
Key on, engine running.

Does WAIT TO START light remain on?

Yes	No
GO to R2.	GO to R3.

R2 CHECK CIRCUIT 464 (BK/PK) FOR SHORT

Key off.
Disconnect PCM.
Key on, engine off.

Is WAIT TO START light on?

Yes	No
SERVICE ground short in Circuit 464 (BK/PK) between WAIT TO START light and PCM. RERUN Scan Tool Diagnostic Test.	REPLACE PCM. RERUN Scan Tool Diagnostic Test.

R3 CHECK INTERMITTENT P0381

A Continuous DTC P0381 is set when the PCM detects a malfunction in the WAIT TO START light circuit.
Possible causes:

intermittently open/grounded circuit or fuse.
intermittently open WAIT TO START light

Key off.
Key on.

Does WAIT TO START light come on for at least 1 second?

Yes	No
Concern is intermittent. GO to R9.	GO to R4.

R4 CHECK FUSE FOR OPEN

Key off.
Check fuse (F-Series — Fuse 17, Econoline — Fuse 18) for continuity.

Is fuse OK?

Yes	No
GO to R5.	GO to R6.

R5 CHECK WARNING LIGHT BULB FOR OPEN

Disconnect WAIT TO START light.
Check bulb for continuity.

Is bulb OK?

Yes	No
GO to R7.	REPLACE bulb. RERUN Scan Tool Diagnostic Test.

R6 CHECK CIRCUIT 640 (R/Y) FOR GROUND SHORT

Disconnect WAIT TO START light.
Measure resistance between Circuit 640 (R/Y) and chassis ground.

Is resistance greater than 10,000 ohms?

Yes	No
REPLACE fuse. RERUN Scan Tool Diagnostic Test.	SERVICE ground short in Circuit 640 (R/Y). REPLACE fuse. RERUN Scan Tool Diagnostic Test.

R7 CHECK FOR OPEN CIRCUIT 640 (R/Y)

Key off.
Disconnect WAIT TO START light.
Key on, engine off.
Measure voltage on Circuit 640 (R/Y) at warning light harness connector.

Is B+ present?

Yes	No
GO to R8.	SERVICE open in Circuit 640 (R/Y) between fuse and WAIT TO START light. RERUN Scan Tool Diagnostic Test.

R8 CHECK FOR OPEN IN CIRCUIT 464 (BK/PK)

Disconnect PCM.
Install breakout box.
Measure resistance in Circuit 464 (BK/PK) between the WAIT TO START light and Pin 80 (49 State except Econoline) or Pin 70 (California and all Econoline) on the breakout box.

Is resistance less than 5 ohms?

Yes	No
REPLACE PCM. RERUN Scan Tool Diagnostic Test.	SERVICE open in Circuit 464 (BK/PK). RERUN Scan Tool Diagnostic Test.

R9 CONTINUOUS P0381 CODE

Clear Continuous DTC P0381.

Does P0381 return in Continuous after road test?

Yes	No
GO to R10.	Code was not cleared after a previous repair.

R10 CHECK FOR CODE P0381 AFTER ROAD TEST

Did the WAIT TO START light come on or flicker on and off during road test?

Yes	No
SERVICE Circuit 464 (BK/PK) intermittently shorting to ground.	GO to R11.

R11 CHECK FOR INTERMITTENTLY OPEN CIRCUIT

Install breakout box. Leave PCM disconnected.
Inspect PCM connector for loose or backing out pins.
Ground test Pin 80 (49 State except Econoline) or test Pin 70 (California and all Econoline).
Tap on dashboard. Shake harness under dash and under hood between the 76-way connector and PCM connector.

Does the WAIT TO START light flicker on and off?

Yes	No
SERVICE an intermittently open light bulb or circuit between fuse and PCM connector.	If unable to find an intermittent short or open, REPLACE PCM.