Hummer H1 Service Manual page 1152

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DTC P0380 - Glow Plug Circuit Performance
Step
10 Turn the ignition ON with the engine OFF. Verify that the glow plug relay control
harness is disconnected. With a DMM connected to ground, probe the glow plug
relay control circuit (466 YL) at the glow plug relay harness connector. Use a scan
tool to command the glow plugs ON and OFF.
Does the DMM display a voltage near the first specified value with the glow plugs
commanded ON and near the the second specified voltage with glow plugs com-
manded OFF?
11 Is the voltage equal to or more than the specified value all the time?
12 Turn the ignition ON leaving the engine OFF. Recconect the glow plug relay control
harness. With a DMM connected to ground, backprobe the glow plug relay signal
circuit (506 LB) at the PCM harness connector. Use a scan tool to command the
glow plugs ON. Observe the DMM while the glow plugs are commanded ON.
Is the voltage at the specified value?
13 Turn the ignition OFF. Disconnect the right and left bank glow plug output circuit
connectors at the glow plug relay. With an unpowered test lamp connected to B+,
probe each circuit.
Does each circuit turn ON the test lamp?
14 Turn the ignition OFF. Disconnect each glow plug connector at the glow plug that
did not illuminate the test lamp. With an unpowered test lamp connected to B+,
probe the terminal on the glow plug.
Does each glow plug illuminate the test lamp?
15 Turn the ignition OFF. Disconnect each glow plug connector at the glow plug. With
an unpowered test lamp connected to B+, probe each circuit at the glow plug output
connectors.
Is the test lamp OFF at each of the circuits?
16 Repair an open or a short to ground in the glow plug relay ignition feed circuit
(CKT 239 PK).
Did you complete the repair?
17 Repair any opens or poor connections in the glow plug relay ground circuit (BK).
Did you complete the repair?
18 Inspect the glow plug relay control circuit (466 YL) for an open or short to ground.
If the glow plug relay control circuit is open or shorted to ground, repair as neces-
sary.
Did you find and correct the condition?
19 Inspect the glow plug relay control circuit (CKT 466 YL) for a proper connection at
the PCM and replace the terminal if necessary.
Did you find an improper connection and make the necessary repair?
20 Inspect the glow plug relay signal circuit (CKT 506 LB) for an open or short to
ground. If the glow plug relay signal circuit is open or shorted to ground, repair as
necessary.
Did you find and correct the condition?
21 Inspect the glow plug relay signal circuit (CKT 506 LB) for a proper connection at
the PCM and replace the terminal if necessary.
Did you find an improper connection and make the necessary repair?
22 Test for a short to voltage in the glow plug relay signal circuit (CKT 506 LB).
Did you find the improper condition?
23 Test for a short to voltage in the glow plug relay control circuit (CKT 466 YL) .
Did you find and correct the condition?
24 Repair the open or poor connection on the battery feed circuit.
Did you complete the repair?
25 Replace any glow plug that did not illuminate the test lamp.
Did you complete the repair?
05745159
Action
PCM/Tech 1 Scan Tool 87
Value Yes
9-12 Volts Go to step
12.
0 volts
1.0 Volt Go to step
23.
5.0-5.6 Go to step
Volts 21.
Go to step
26.
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26.
Go to step
20.
Go to step
30.
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30.
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30.
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30.
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30.
Go to
step30.
Go to step
30.
Go to step
30.
Go to step
30.
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30.
No
Go to step
11.
Go to step
18.
Go to step
13.
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14.
Go to step
25.
Go to step
27.
Go to step
19.
Go to step
29.
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28.
Go to step
22.
Go to step
28.
Go to step
29.