Hummer H1 (2006+). Manual - part 79

OBD-160

On-Board Diagnostics

_____________________________________________

DTC P0370 & P0374 High Resolution Circuit (Figure OBD-46)

Figure OBD-46: High Resolution Circuit

Circuit Description

The engine control module (ECM) replicates the signal received from the crankshaft position (CKP) sensor. This signal is sent to
the fuel injection control module (FICM) through the engine speed signal circuit. The FICM uses this replicated signal to generate
injection current and control the recharge of the fuel injection high voltage circuits. When cranking, the FICM has full control of
the fuel injectors. The only input the FICM uses at this time is the engine speed signal from the ECM. The FICM monitors the sig-
nal along with the injection request signals from the ECM after the engine is running. If there is a problem with this signal, a DTC
could set.

Conditions for Setting the DTC

• The FICM does not receive a crank signal, but does receive injection requests from the ECM. OR

• The FICM receives an invalid crank signal from the ECM.

Action Taken When the DTC Sets

• The control module illuminates the malfunction indicator lamp (MIL) when the diagnostic runs and fails.

• The control module records the operating conditions at the time the diagnostic fails. The control module stores this informa-

tion in the Freeze Frame/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.

Diagnostic Aids

A missing high resolution signal will cause a no-start condition. High resistance in the position sensor low reference circuit may
cause this DTC to set. If the condition is intermittent, refer to Intermittent Conditions .

_____________________________________________

On-Board Diagnostics OBD-161

5745804

Step

Action

Value(s)

Yes

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.

Crank the engine.

Observe the Specific DTC information with the scan tool for
the DTC that was set.

Does the scan tool display Last Test Failed?

Go to Step 3

Intermittent Go

To Diagnostic

Aids

NOTE: Use the proper terminal from J 35616-B Connector Test
Adapter Kit.

Turn OFF the ignition.

Disconnect the fuel injection control module (FICM) harness
C76 containing the engine speed signal circuit 660 (LB).

Connect a DVOM between the engine speed signal circuit
660 (LB) and a good ground.

Measure the voltage while cranking the engine.

Does the voltage measure within the specified range?

5.5-6.3

Volts

Go to Step 5

Go to Step 4

Does the voltage measure above the specified range?

5.5-6.3

Volts

Go to Step 6

Go to Step 7

Test for a short to reference voltage on the engine speed signal
circuit 660 (LB) between C76 pin 63 and C86 pin 94.

Did you find and correct the condition?

Go to Step 12

Go to Step 8

Test for a short to voltage in the engine speed signal circuit
660 (LB) between C76 pin 63 and C86 pin 94.

Repair as necessary.

Did you find and correct the condition?

Go to Step 12

Go to Step 10

Test the engine speed signal circuit 660 (LB) and for an open
or a short to ground between C76 pin 63 and C86 pin 94 of
the FICM.

Repair as necessary.

Did you find and correct the condition?

Go to Step 12

Go to Step 10

Test for a poor connection at the FICM.

Did you find and correct the condition?

Go to Step 12

Go to Step 9

Replace the faulty FICM.

Did you complete the replacement?

Go to Step 12

Test for a poor connection at the engine control module (ECM).

Did you find and correct the condition?

Go to Step 12

Replace the faulty ECM.

Did you complete the replacement?

Go to Step 12

OBD-162

On-Board Diagnostics

_____________________________________________

Clear the DTCs with a scan tool.

Turn OFF the ignition for 30 seconds.

Start the engine.

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 2

Go to Step 13

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

_____________________________________________

On-Board Diagnostics OBD-163

5745804

DTC P0381 Wait To Start Control Circuit (Figure OBD-47)

Figure OBD-47: Wait To Start Control Circuit

Circuit Description

Ignition voltage is supplied directly to the wait to start indicator. The engine control module (ECM) controls the lamp by grounding
the control circuit via an internal switch called a driver. The primary function of the driver is to supply the ground for the compo-
nent being controlled. Each driver has a fault line which is monitored by the ECM. When the ECM is commanding a component
ON, the voltage of the control circuit should be low, near 0 volts. When the ECM is commanding the control circuit to a component
OFF, the voltage potential of the circuit should be high, near battery voltage. If the fault detection circuit senses a voltage other
than what is expected, the fault line status will change causing the DTC to set.

Conditions for Setting the DTC

• The ECM detects that the commanded state of the driver and the actual state of the control circuit do not match.

• The condition must be present for a minimum of 5 seconds.

Action Taken When the DTC Sets

• The ECM stores the DTC information in memory.

• The ECM records the operating conditions at the time the DTC sets. The ECM displays the failure information in the Failure

Records on the scan tool.

Conditions for Clearing the DTC

• The history DTC clears after 40 malfunction free warm-up cycles.

• The DTC becomes history when the conditions for setting the DTC are no longer present.

• The ECM receives the clear code command from the scan tool.

Diagnostic Aids

NOTE: Remove any debris from the ECM connector surfaces before servicing the ECM. Inspect the ECM connector gaskets when
diagnosing/replacing the ECM. Ensure that the gaskets are installed correctly. The gaskets prevent water intrusion into the ECM.

Using Freeze Frame and/or Failure Records data may aid in locating an intermittent condition. If you cannot duplicate the DTC,
the information included in the Freeze Frame and/or Failure Records data can aid in determining how many miles since the DTC
set. The Fail Counter and Pass Counter can also aid determining how many ignition cycles the diagnostic reported a pass and/or a
fail. Operate the vehicle within the same freeze frame conditions (RPM, load, vehicle speed, temperature etc.) that you observed.
This will isolate when the DTC failed.

Content .. 77 78 79 80 ..