Hummer H2. Manual — part 1382

Monitored Coolant Temperature - Range: 40-215° C (40-419° F)

This data is the clusters measurement of the engine coolant temperature as provided by the PCM on the
class 2 serial data line.

DIAGNOSTIC TROUBLE CODE (DTC) LIST

Diagnostic Trouble Code (DTC) List

DTC P1258

Circuit Description

The powertrain control module (PCM) uses the engine coolant temperature (ECT) sensor to monitor the engine
for an over temperature condition. This condition occurs when the coolant temperature is above 132° C (270°
F). When an over temperature condition is present, DTC P1258 will set. The PCM will disable 2 groups of 4
cylinders by turning OFF the fuel injectors. By switching between the 2 groups of cylinders, the PCM is able to
reduce the temperature of the coolant.

Conditions for Running the DTC

z

DTCS P0117, P0118, P1114, and P1115 are not active.

z

The engine is running.

Conditions for Setting the DTC

The engine coolant temperature is above 132° C (270° F) for 10 seconds or more.

Action Taken When the DTC Sets

z

The PCM will illuminate the malfunction indicator Lamp (MIL) during the first trip in which the
diagnostic test has been run and failed.

z

The PCM will signal the IPC to turn ON the Service Engine Soon indicator.

z

The PCM will alternately disable two groups of four cylinders by turning OFF the fuel injectors.

z

The PCM will store conditions which were present when the DTC set as Freeze Frame and File Records
data.

Conditions for Clearing the MIL/DTC

z

The PCM will turn the MIL OFF after 3 consecutive trips that the diagnostic has been run and passed.

z

The history DTC will clear after 40 consecutive warm-up cycles have occurred without a malfunction.

z

The DTC can be cleared by using the scan tool Clear DTC Information function.

DTC

Diagnostic Procedure

Module

P1258

DTC P1258

PCM

2004 Hummer H2

2004 ENGINE Engine Cooling - Hummer H2

DTC P1258

SYMPTOMS - ENGINE COOLING

Visual/Physical Inspection

z

Inspect for aftermarket devices which could affect the operation of the Cooling System. Refer to
Checking Aftermarket Accessories in Wiring Systems.

z

Inspect the easily accessible or visible system components for obvious damage or conditions which could
cause the symptom.

z

Inspect the surge tank reservoir for the proper coolant level.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for
Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

z

Engine Overheated Indicator Always On

z

Engine Coolant Temperature Indicator Always On

z

Coolant Heater Inoperative

z

Engine Overheating

z

Loss of Coolant

z

Thermostat Diagnosis

z

Engine Fails To Reach Normal Operating Temperature

z

Fan Clutch Diagnosis

z

Low Engine Coolant Indicator Always On

ENGINE OVERHEATED INDICATOR ALWAYS ON

Step

Action

Yes

No

Connector End View Reference: Cooling System Connector End Views

1

Was the Diagnostic System Check for
Engine Cooling performed?

Go to Step 2

Go to Diagnostic System Check

- Engine Cooling

2

Check the engine cooling fan for proper
operation.
Is the engine cooling fan operative?

Go to Engine

Overheating

Go to Symptoms - Engine

Cooling

IMPORTANT: Review the system operation in order to familiarize yourself with the system

functions. Refer to Cooling System Description and Operation .

2004 Hummer H2

2004 ENGINE Engine Cooling - Hummer H2

Engine Overheated Indicator Always On

ENGINE COOLANT TEMPERATURE INDICATOR ALWAYS ON

Engine Coolant Temperature Indicator Always On

Step

Action

Yes

No

Connector End View Reference:Engine Cooling Schematics
DEFINITION: One of the following engine coolant temperature indicators is always On: Engine
Coolant, Engine Coolant Hot/Idle Engine, Engine Hot-AC Off, Engine Overheated/Stop Engine.

1

Did you perform the Engine Cooling Diagnostic
System Check?

Go to Step 2

Go To Diagnostic System

Check - Engine Cooling

2

Start the engine.
Does the Engine Coolant Temperature indicator
illuminate?

Go to Step 3

Go to Testing for

Intermittent Conditions and

Poor Connections in Wiring

Systems

3

1. Install a scan tool.

2. With the scan tool, observe the engine

coolant temperature parameter in the
powertrain control module (PCM) data list.

Does the scan tool indicate that the coolant
temperature is within the temperature range
shown on the temperature gauge?

Go to Engine

Overheating

Go to Step 4

4

Replace the instrument panel cluster (IPC). Refer
to Instrument Panel Cluster (IPC)
Replacement in Instrument Panel, Gauges, and
Console.
Did you complete the replacement?

Go to Step 5

-

5

Operate the system in order to verify the repair.
Did you correct the condition?

System OK

Go to Step 2

Step

Action

Yes

No

Connector End View Reference:Cooling System Connector End Views
DEFINITION: One of the following engine coolant temperature indicators is always On: Engine
Coolant, Engine Coolant Hot/Idle Engine, Engine Hot-AC Off, Engine Overheated/Stop Engine.

1

Did you perform the Engine Cooling Diagnostic
System Check?

Go to Step 2

Go To Diagnostic System

Check - Engine Cooling

2

Start the engine.
Does the Engine Coolant Temperature indicator
illuminate?

Go to Step 3

Go to Testing for

Intermittent Conditions and

Poor Connections in Wiring

Systems

3

1. Install a scan tool.

2. With the scan tool, observe the engine

coolant temperature parameter in the
powertrain control module (PCM) data list.

2004 Hummer H2

2004 ENGINE Engine Cooling - Hummer H2

LOW ENGINE COOLANT INDICATOR ALWAYS ON

Low Engine Coolant Indicator Always On

Does the scan tool indicate that the coolant
temperature is within the temperature range
shown on the temperature gauge?

Go to Engine

Overheating

Go to Step 4

4

Replace the instrument panel cluster (IPC). Refer
to Instrument Panel Cluster (IPC)
Replacement in Instrument Panel, Gauges, and
Console.
Did you complete the replacement?

Go to Step 5

-

5

Operate the system in order to verify the repair.
Did you correct the condition?

System OK

Go to Step 2

Step

Action

Yes

No

Connector End View Reference:Engine Cooling Schematics

1

Did you perform the Engine Cooling Diagnostic System
Check?

Go to

Step 2

Go to Diagnostic System

Check - Engine Cooling

2

1. Verify that the engine coolant is at the proper level.

2. Turn ON the ignition, with the engine OFF.

Does the instrument panel cluster (IPC) display Low
Engine Coolant?

Go to

Step 3

Go to Testing for

Intermittent Conditions

and Poor Connections in

Wiring Systems

3

1. Install a scan tool.

2. With a scan tool, view the Coolant Level Switch data

in the Engine Data 2 data list.

Does the scan tool display Low?

Go to

Step 4

Go to Step 7

4

1. Disconnect the coolant level sensor electrical

connector.

2. Connect a 3-amp fused jumper between the coolant

level switch signal circuit of the coolant level sensor
electrical connector and the ground circuit of the
coolant level sensor electrical connector.

3. With a scan tool, view the Coolant Level Switch data

in the Engine Data 2 data list.

Does the scan tool display OK?

Go to

Step 8

Go to Step 5

5

1. Connect a 3-amp fused jumper between the coolant

level switch signal circuit of the coolant level sensor
electrical connector and a good ground.

2. With a scan tool, view the Coolant Level Switch data

2004 Hummer H2

2004 ENGINE Engine Cooling - Hummer H2