GM Service Manual Online
For 1990-2009 cars only

Circuit Description

The following DTCs are for the battery voltage sensors located in the energy storage box (ESB) on each battery:

    • P1A24 is for the hybrid battery 1 voltage.
    • P1A2B is for the hybrid battery 2 voltage.
    • P1A32 is for the hybrid battery 3 voltage.

Battery voltage sensors allow the energy storage control module (ESCM) to monitor the voltage of the batteries in the energy storage box. The batteries apply voltage to internal input resistors that are connected to the signal circuits of the battery voltage sensors. The module provides ground to the battery voltage sensors through the reference circuit. The ESCM monitors the voltage drop across the battery voltage sensors and uses the inputs for hybrid calculations. When the battery voltage is high, the resistances of the sensors are high and the voltage signals are high. When the battery voltage is low, the resistances of the sensors are low and the voltage signals are low. The out of range rationality diagnostics (P1A24, P1A2B, P1A32) determine if each sensor is within a certain amount of the average of the sensors. These faults are only run when during discharge, and when the 42V bus correlation is valid and stable

DTC Descriptors

This diagnostic procedure supports the following DTCs:

    • P1A24 is for the hybrid battery 1 voltage.
    • P1A2B is for the hybrid battery 2 voltage.
    • P1A32 is for the hybrid battery 3 voltage.

Conditions for Running the DTC

    • The ignition is ON.
    • The engine has been running for 30 seconds.

Conditions for Setting the DTC

    • P1A24 is for the hybrid battery 1 voltage correlation fault.
    • P1A2B is for the hybrid battery 2 voltage correlation fault.
    • P1A32 is for the hybrid battery 3 voltage correlation fault.

Action Taken When the DTC Sets

    • The powertrain control module (PCM) stores the DTC information into memory when the diagnostic runs and fails.
    • The malfunction indicator lamp (MIL) will not illuminate.
    • The driver information center, if equipped, may display a message.

Conditions for Clearing the DTC

    • The DTC will become history if the ESCM no longer detects a fault.
    • The history DTC will clear after 40 fault-free ignition cycles.
    • The DTC can be cleared with a scan tool.

Disconnected sensor

Expected Result Displayed on Scan Tool

Voltage Sensor 1

    • Battery 1 Voltage 12.5 Volts
    • Battery 2 Voltage 12.5 Volts
    • Battery 3 Voltage 12.5 Volts
    • Battery Pack Voltage 37.5 Volts

Voltage Sensor 2

    • Battery 1 Voltage 0 Volts
    • Battery 2 Voltage 25 Volts
    • Battery 3 Voltage 12.5 Volts
    • Battery Pack Voltage 37.5 Volts

Voltage Sensor 3

    • Battery 1 Voltage 12.5 Volts
    • Battery 2 Voltage 0 Volts
    • Battery 3 Voltage 37.5 Volts
    • Battery Pack Voltage 37.5 Volts

Voltage Sensor 4

    • Battery 1 Voltage 12.5 Volts
    • Battery 2 Voltage 12.5 Volts
    • Battery 3 Voltage 0 Volts
    • Battery Pack Voltage 0 Volts

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Verifies that the voltage displayed is not within the calibrated range.

  2. Tests for the proper operation of the circuit in the high voltage range.

  3. Tests for the proper operation of the circuit in the low voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to voltage.

Step

Action

Values

Yes

No

Schematic Reference: Starting and Charging Schematics

Connector End View Reference: Engine Electrical Connector End Views

1

Did you perform the Diagnostic System Check - Vehicle?

--

Go to Step 2

Go to Diagnostic Starting Point - Engine Electrical in Engine Electrical

2

Test each battery for low charge or over charge. Refer to battery testing and inspection Battery Inspection/Test .

Do the batteries test good?

--

Go to Step 3

Go to Step 11

3

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, observe the appropriate Battery Voltage parameter in the battery energy control module (BECM) data list.

Does the scan tool indicate that all 3 battery voltage parameters are within the specified range of each other?

-1 V

Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Disconnect the appropriate battery voltage sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Battery Voltage Data parameters.
  5. Compare the voltage parameters to the above table.

Do the parameters fall within the specified values in the above table?

--

Go to Step 5

Go to Step 6

5

  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the signal circuit of the appropriate battery voltage sensor and the reference circuit of the battery voltage sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the appropriate Battery Voltage data parameter.

Does the scan tool indicate that the Battery 3 Voltage Data parameter is less than the specified value?

12 V

Go to Step 9

Go to Step 7

6

Test the signal circuit of the appropriate battery voltage sensor for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 14

Go to Step 10

7

Test the signal circuit of the appropriate battery voltage sensor for 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 14

Go to Step 8

8

Test the reference circuit of the appropriate battery voltage 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 14

Go to Step 10

9

Inspect for poor connections at the harness connector of the appropriate battery voltage 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 14

Go to Step 12

10

Inspect for poor connections at the harness connector of the energy storage control module (ESCM). 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 14

Go to Step 13

11

Replace the appropriate battery. Refer to Generator Battery Replacement .

Did you complete the replacement?

--

Go to Step 14

--

12

Replace the appropriate battery voltage sensor. Refer to the battery voltage sensor replacement procedure Battery Boost Resistor Replacement

Did you complete the replacement?

--

Go to Step 14

--

13

Replace the ESCM. Refer to Generator Battery Control Module Replacement in Engine Electrical for replacement, setup, and programming.

Did you complete the replacement?

--

Go to Step 14

--

14

  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 3

System OK