Hummer H1 (2006+). Manual - part 93

OBD-216

On-Board Diagnostics

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DTC P0670 Glow Plug Control Module Control Circuit (Figure OBD-61)

Figure OBD-61:   Glow Plug Control Module Circuit

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 On-Board Diagnostics  OBD-217

5745804

Circuit Description

The glow plug controller has the ability to perform internal diagnostics for voltage and output state of the glow plugs. If the glow
plug controller senses an open in the main battery supply to the glow plug controller, or a condition with any of the glow plug
driver circuits, the glow plug controller will send an error message to the engine control module (ECM). 

Conditions for Setting the DTC

The glow plug controller detects an open to the main battery supply for the glow plugs, or an open in all 8 glow plug circuits for
less than 1 second.

Action Taken When the DTC Sets 

• The control module illuminates the malfunction indicator lamp (MIL) on the second consecutive ignition cycle that the diag-

nostic runs and fails. 

• The control module records the operating conditions at the time the diagnostic fails. The first time the diagnostic fails, the

control module stores this information in the Failure Records. If the diagnostic reports a failure on the second consecu-
tive ignition cycle, the control module records the operating conditions at the time of the failure. The control module 
writes the operating conditions to the Freeze Frame and updates the Failure Records. 

Conditions for Clearing the MIL/DTC 

• The control module turns OFF the malfunction indicator lamp (MIL) after 3 consecutive ignition cycles that the diagnostic 

runs and does not fail. 

• A current DTC, Last Test Failed, clears when the diagnostic runs and passes. 

• A history DTC clears after 40 consecutive warm-up cycles, if no failures are reported by this or any other emission related 

diagnostic.

• Clear the MIL and the DTC with a scan tool. 

Step

Action

Value(s)

Yes

No

    1

NOTE: Before clearing DTC(s) use the scan tool “Capture info”
to record Freeze Frame and Failure Records for reference, as data
will be lost when “Clear Info” function is used 

Was the “On-Board Diagnostic (OBD) System Check” per-
formed?

Go to step 2.

Go to OBD Sys-

tem Check.

    2

1.

Observe the Freeze Frame/Failure Records for this DTC.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Operate the vehicle within the Conditions for Running the 
DTC. You may also operate the vehicle within the conditions 
that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 3 

Go to Intermit-

tent Conditions 

    3

Is DTC P0671-P0678 set?

Go to Step 4

Go to Step 5

OBD-218

On-Board Diagnostics

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    4

NOTE: The DVOM and test leads must be calibrated to 0 ohms
in order to prevent misdiagnosis. Perform this test with the
DVOM. Refer to the DVOM User Manual for calibration proce-
dure.

1.

Turn OFF the ignition.

2.

Disconnect the glow plug controller harness connector.

3.

Measure the resistance from the ground circuit PK/YL at the 
glow plug controller harness C85 pin 11 and a good ground 
on the engine with a DVOM.

Does the DVOM display a resistance below the specified value?

1 ohms

Go to Step 6

Go to Step 7

    5

1.

Turn OFF the ignition.

2.

Disconnect the main battery circuit from the glow plug con-
troller.

3.

Probe the main battery + circuit with a test lamp that is con-
nected to a good ground. 

Does the test lamp illuminate?

Go to Step 6

Go to Step 8

    6

Test for an intermittent and for a poor connection at the harness
connector of the glow plug controller. Did you find and correct
the condition?

Go to Step 11 

Go to Step 10

    7

Repair the ground circuit (PK/YL) of the glow plug harness be-
tween the glow plug controller C85 pin 11 and the engine ground
G1 for high resistance. 

Did you complete the repair?

Go to Step 9 

    8

Repair the open or the short to ground in the battery positive volt-
age circuit between the glow plug controller and the battery.

Did you complete the repair?

Go to Step 11

    9

Replace the faulty glow plugs. 

Did you complete the replacement?

Go to Step 11

    10

Replace the faulty glow plug controller. 

Did you complete the replacement?

Go to Step 11

    11

1.

Clear the DTCs with a scan tool.

2.

Turn OFF the ignition for 30 seconds.

3.

Start the engine.

4.

Operate the vehicle within the Conditions for Running the 
DTC. You may also operate the vehicle within the conditions 
that you observed from the Freeze Frame/Failure Records.

Did the DTC fail this ignition?

Go to Step 1 

Go to Step 12

   12

Using the Scan Tool select “Capture Info,” Review Info.” Are
any DTC’s displayed that have not been diagnosed?

Go to the appli-

cable DTC 

table.

System OK.

Step

Action

Value(s)

Yes

No

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 On-Board Diagnostics  OBD-219

5745804

DTC P0671-P0678 Glow Plug Control Circuit (Figure OBD-62)

Figure OBD-62:   Glow Plug Control Circuit