Hummer H1 Service Manual page 1151

86 PCM/Tech 1 Scan Tool
Signal
Voltage
5.0-5.6
2.3-2.8
1.3-1.8
0.8-1.4
Less than 1.1
DTC P0380 - Glow Plug Circuit Performance
Step
1 Before clearing any DTC's, use the scan tool Capture Info to save the Freeze Frame
and Failure Records for reference. The PCM's data is deleted once the Clear Info
function is used.
Did you perform the On-Board Diagnostic (OBD) System Check?
2 If DTC P0380 set after a PCM reflash.
Connect a scan tool. Turn the ignition ON leaving the engine OFF. Observe the
Glow Plug System Type parameter on the scan tool.
Does the scan tool display the Glow Plug System Type as California?
3 Connect a scan tool. Turn the ignition ON leaving the engeine OFF. Use the scan
tool to command the glow plugs ON and OFF. Observe the Glow Plug System Type
parameter on the scan tool.
Does the digital multimeter (DMM) display a voltage near the first specified value
with the glow plug comanded ON and near the second specified value with the glow
plug commanded OFF?
4 Does the scan tool display a glow plug voltage greater than the specified value?
5 Does the scan tool display a glow plug voltage greater than the specified value?
6 Turn the ignition ON leaving the engine OFF. Touch the battery feed stud on the
glow plug controller with an unpowered test lamp connected to ground.
Is the test light ON?
7 The DTC is intermittent. If any additional DTC's were stored, refer to those
table(s).
Were ther any additional DTC's stored?
8 Disconnect the glow plug relay control connector. Turn the ignition ON with the
engine OFF. With an unpowered test lamp connected to ground, probe the glow plug
relay harness ignition feed circuit (CKT 239 PK).
Is the test light ON?
9 Turn the ignition ON with the engine OFF. Connect an unpowered test lamp to B+,
probe the glow plug relay ground circuit (BK).
Is the test light ON?
_____________________________________________________
Glow Plugs
None
1
2
3
4 or more
Action
Test Description
Number(s) below refer to the number(s) on the diagnostic ta-
ble.
3-This step will determine if P0380 is a hard failure.
4-This step will determine if there is a short to voltage on the
signal circuit.
8-This step will determine if there is ignition voltage at the
glow plug relay.
10-This step will determine if the glow plug control circuit and
the PCM are working properly.
11-This step will determine if if there is a short to voltage an
the relay control circuit.
13-This step will determine if the glow plugs or the glow plug
harness is causing the P0380 DTC.
Value Yes
Go to step
2.
Go to step
3. (LINK-GO
TO-REPAI
R-609502)
Glow Plug
5.0-5.6 Go to step Go to step
Volts 7.
0.9-1.5
Volts
5.6 Volts Go to step Go to step
21.
0.3 Volts Go to step Go to step
10.
Go to step Go to step
8.
Go to the
applicable Diagnostic
DTC table.
Go to step Go to step
9.
Go to step Go to step
10.
®
No
Go to
System
Type
Relearn
4.
5.
6.
25.
Go to
Aids.
16.
17.