Hummer H2. Manual - part 763

DTC C0191

Circuit Description

The EBCM provides power 5 volts reference to the longitudinal accelerometer. The longitudinal accelerometer
converts the change in vehicle motion, or inertia, into a voltage signal. This signal is sent to the EBCM.

The voltage signal ranges, from 2.4 to 2.6 volts at zero speed change, constant motion, or stationary. The
longitudinal accelerometer voltage signal drops when the vehicle is under acceleration. The longitudinal
accelerometer voltage signal increases when the vehicle is under deceleration. The usable output voltage range
for the longitudinal accelerometer is 0.48-4.82 volts. The longitudinal accelerometer sensor bias compensates
for sensor mounting alignment errors and electronic signal errors.

Conditions for Running the DTC

The ignition is ON.

2. With the scan tool, observe the Brake Switch Status parameter

in the ABS data list.

Does the Brake Switch Status parameter display Applied?

Go to

Step 4

Go to Step 3

Test the signal circuit of the stop lamp switch for an open. Refer to
Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to

Step 9

Go to Step 7

Press the brake pedal.
Are all of the stoplamps OFF?

Go to

Step 5

Go to Diagnostic

Aids

Test the feed circuit of the stop lamps for an open or high resistance.
Refer to Circuit Testing and Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to

Step 9

Go to Step 6

Test the ground circuit of the stop lamps for an open or high
resistance. Refer to Circuit Testing and Wiring Repairs in Wiring
Systems.
Did you find and correct the condition?

Go to

Step 9

Go to Diagnostic

Aids

Inspect for poor connections at the harness connector of the EBCM.
Refer to Testing for Intermittent Conditions and Poor
Connections and Connector Repairs in Wiring Systems.
Did you find and correct the condition?

Go to

Step 9

Go to Step 8

Replace the EBCM. Refer to Electronic Brake Control Module
Replacement .
Did you complete the replacement?

Go to

Step 9

1. Use the scan tool in order to clear the DTCs.

2. Operate the vehicle within the Conditions for Running the DTC

as specified in the supporting text.

Does the DTC reset?

Go to

Step 2

System OK

2004 Hummer H2

2004 BRAKES Anti-Lock Brake System - Hummer H2

The DTC can be set after system initialization.

Conditions for Setting the DTC

Voltage at the longitudinal accelerometer signal output to the EBCM falls outside the 0.48 V - 4.82 V range for
more than 100 milliseconds.

Action Taken When the DTC Sets

A malfunction DTC is set

TCS is disabled

The ABS warning indicator turns ON.

Conditions for Clearing the DTC

The condition for the DTC is no longer present

A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no
longer present.

Using a scan tool.

Diagnostic Aids

A thorough inspection of the wiring system and connectors be performed. Failure to carefully and fully
inspect the wiring system and connectors may result in misdiagnosis which may result in replacing good
parts and the reappearance of the malfunction.

Inspection for poor connections, broken insulation, or a wire that is broken inside the insulation.

If an intermittent malfunction exists refer to Testing for Intermittent Conditions and Poor
Connections in Wiring Systems.

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

2: Tests for specified voltage on the LNG accelerometer signal circuit.

3: Checks to see if voltage was below or above specified voltage.

4: Checks to see if voltage was above specified voltage.

5: Checks to see if voltage was below specified voltage.

6: Checks to see if voltage was above specified voltage.

7: Checks to see if resistance of ground circuit is less than 5 ohms.

8: Tests for a short to voltage on the 5 volt reference circuit.

9: Tests for a short to ground, a high resistance, or an open in the 5 volt reference circuit.

10: Tests for a short to ground, a high resistance, or an open in the lateral accelerometer signal circuit.

11: Tests for a short to voltage in the lateral accelerometer signal circuit.

2004 Hummer H2

2004 BRAKES Anti-Lock Brake System - Hummer H2

12: Tests for a high resistance or an open in the ground circuit.

13: Checks the LNG accelerometer sensor connector for poor connections.

DTC C0191

Step

Action

Value

(s)

Yes

Schematic Reference: ABS Schematics
Connector End View Reference:ABS Connector End Views

Did you perform the ABS Diagnostic System Check?

Go to Step 2

Go to

Diagnostic

System Check -

ABS

1. Turn OFF the ignition.

2. Disconnect the EBCM.

3. Install the J 39700 universal pinout box with the.

See Special Tools and Equipment . J 39700-530
cable adapter between the EBCM and the EBCM
harness connector.

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

5. Using the J 39200 , measure the voltage between

pin 10 and pin 15 of the J 39700 universal pinout
box. See Special Tools and Equipment .

Is the voltage within the specified value?

0.48 V

- 4.82

Go to

Diagnostic

Aids

Go to Step 3

1. Reconnect the LNG accelerometer sensor.

2. Using a J 39200 , measure the voltage between pin

10 and pin 15 of the J 39700 universal pinout box.
See Special Tools and Equipment .

Is the voltage less than the specified value?

4.82 V

Go to Step 4

Go to Step 11

Using a DMM, measure the voltage between pin 10 and
pin 15 of the J 39700 universal pinout box. See Special
Tools and Equipment .
Is the voltage greater than the specified value?

0.48 V

Go to Step 5

Go to Step 10

Using a DMM, measure the voltage between the 5 volt
reference circuit pin 28 and the ground circuit pin 15 on
the J 39700 universal pinout box. See Special Tools and
Equipment .
Does the voltage measure less than the specified value?

2 V

Go to Step 9

Go to Step 6

Using a DMM, measure the voltage between the 5 volt
reference circuit pin 28 and ground circuit pin 15 on the J
39700 universal pinout box. See Special Tools and
Equipment .

3 V

2004 Hummer H2

2004 BRAKES Anti-Lock Brake System - Hummer H2

Does the voltage measure greater than the specified
voltage?

Go to Step 8

Go to Step 7

1. Turn OFF the ignition.

2. Disconnect the negative battery cable.

3. Measure the resistance from the ground circuit of

the LNG accelerometer to a good ground.

Does the resistance measure less than the specified value?

5 ohm

Go to Step

Go to Step 12

Test the 5 volt reference circuit of the LNG accelerometer
sensor for a short to voltage. Refer to Circuit Testing and
Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step

Go to Step 13

Test the 5 volt reference circuit of the LNG accelerometer
sensor for a short to ground, a high resistance, or an open.
Refer to Circuit Testing and Wiring Repairs in Wiring
Systems.
Did you find and correct the condition?

Go to Step

Go to Step 10

Test the LNG accelerometer signal circuit of the LNG
accelerometer sensor for a short to ground, a high
resistance, or an open. Refer to Circuit Testing and
Wiring Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step

Go to Step 13

Test the LNG accelerometer signal circuit of the
yaw/lateral accelerometer sensor for a short to voltage.
Refer to Circuit Testing and Wiring Repairs in Wiring
Systems.
Did you find and correct the condition?

Go to Step

Go to Step 13

1. Disconnect the EBCM.

2. Test the ground circuit of the LNG accelerometer

sensor for a high resistance or an open. Refer to
Circuit Testing and Wiring Repairs in Wiring
Systems.

Did you find and correct the condition?

Go to Step

Go to Step 13

Inspect for poor connections at the harness connector of
the LNG accelerometer sensor. Refer to Testing for
Intermittent Conditions and Poor Connections and
Connector Repairs in Wiring Systems.
Did you find and correct the condition?

Go to Step

Go to Step 15

Inspect for poor connections at the harness connector of
the EBCM. Refer to Testing for Intermittent Conditions
and Poor Connections and Connector Repairs in
Wiring Systems.
Did you find and correct the condition?

Go to Step

Go to Step 16

2004 Hummer H2

2004 BRAKES Anti-Lock Brake System - Hummer H2

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