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Discussion Starter #3
My truck seems to be running A ok...but my check engine light stays on. Should i change my DPF and program it back to stock before i take it to the dealership? I am still under waranty
 

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Spartan, True Performance
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P0684 - Glow Plug Control Module (GPCM) to Powertrain Control Module (PCM) Communication Circuit Range/Performance
Description: During the glow plug system check, the PCM enables the GPCM and monitors the GPCM/PCM communication circuit for a response. The DTC sets when the PCM stops receiving messages or receives an error message from the GPCM over the communication circuit.
Possible Causes: • GPCM/PCM communication circuit open in the harness
• GPCM/PCM communication circuit short to ground in the harness
• GPCM/PCM communication circuit short to voltage in the harness
Diagnostic Aids: This DTC may be set as a result of the concern with GPCM control circuit. Diagnose DTC P0670 before diagnosing DTC P0684.

P0670 - Glow Plug Control Module (GPCM) Control Circuit/Open
Description: The powertrain control module (PCM) carries out a functional key ON, engine running
(KOER) self-test for the glow plug system. During that test the PCM enables the GPCM
which monitors glow plug control circuit for concerns. When the GPCM detects a concern
with a glow plug control circuit, it sends a message to the PCM, which sets this DTC.
Possible Causes: • Glow plug control circuit open in the harness
• Glow plug control circuit short to ground in the harness
• Glow plug control circuit short to voltage in the harness
Diagnostic Aids: Check the wiring harness for an open or a short circuit.
 

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Registered
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Discussion Starter #11
P0684 - Glow Plug Control Module (GPCM) to Powertrain Control Module (PCM) Communication Circuit Range/Performance
Description: During the glow plug system check, the PCM enables the GPCM and monitors the GPCM/PCM communication circuit for a response. The DTC sets when the PCM stops receiving messages or receives an error message from the GPCM over the communication circuit.
Possible Causes: • GPCM/PCM communication circuit open in the harness
• GPCM/PCM communication circuit short to ground in the harness
• GPCM/PCM communication circuit short to voltage in the harness
Diagnostic Aids: This DTC may be set as a result of the concern with GPCM control circuit. Diagnose DTC P0670 before diagnosing DTC P0684.

P0670 - Glow Plug Control Module (GPCM) Control Circuit/Open
Description: The powertrain control module (PCM) carries out a functional key ON, engine running
(KOER) self-test for the glow plug system. During that test the PCM enables the GPCM
which monitors glow plug control circuit for concerns. When the GPCM detects a concern
with a glow plug control circuit, it sends a message to the PCM, which sets this DTC.
Possible Causes: • Glow plug control circuit open in the harness
• Glow plug control circuit short to ground in the harness
• Glow plug control circuit short to voltage in the harness
Diagnostic Aids: Check the wiring harness for an open or a short circuit.
That looks like a foreign language! hahah Should i take it in or is it minor? :confused:
 

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IM OUT!!!
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That looks like a foreign language! hahah Should i take it in or is it minor? :confused:

what mick is trying to imply, is that most likely its 1 code triggering the other. try addressing the p0670 glitch first before doing the other.
not being plugged in, grounded or low reading can cause it. most of the time its due to a faulty sensor.
 

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IM OUT!!!
Joined
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4,548 Posts
P0684 - Glow Plug Control Module (GPCM) to Powertrain Control Module (PCM) Communication Circuit Range/Performance
Description: During the glow plug system check, the PCM enables the GPCM and monitors the GPCM/PCM communication circuit for a response. The DTC sets when the PCM stops receiving messages or receives an error message from the GPCM over the communication circuit.
Possible Causes: • GPCM/PCM communication circuit open in the harness
• GPCM/PCM communication circuit short to ground in the harness
• GPCM/PCM communication circuit short to voltage in the harness
Diagnostic Aids: This DTC may be set as a result of the concern with GPCM control circuit.

fix DTC P0670 first
Diagnose DTC P0670 before diagnosing DTC P0684.
P0670 - Glow Plug Control Module (GPCM) Control Circuit/Open
Description: The powertrain control module (PCM) carries out a functional key ON, engine running
(KOER) self-test for the glow plug system. During that test the PCM enables the GPCM
which monitors glow plug control circuit for concerns. When the GPCM detects a concern
with a glow plug control circuit, it sends a message to the PCM, which sets this DTC.

how to check for stuff going bad-
Possible Causes: • Glow plug control circuit open in the harness
• Glow plug control circuit short to ground in the harness
• Glow plug control circuit short to voltage in the harness
Diagnostic Aids: Check the wiring harness for an open or a short circuit.

hope this helps
 
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