GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Isuzu 🢒 2008 🢒 I-370 🢒 Safety and Security 🢒 Immobilizer 🢒 DTC B2957, B2958, B2960, or B3033

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    • Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

DTC Descriptors

DTC B2957: Security System Sensor Data Circuit Low

DTC B2958: Security System Sensor Data Circuit High

DTC B2960: Security System Sensor Data Incorrect but Valid

DTC B3033: Security System Indicates Tamper

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Off/Run/Crank Voltage

B1442

B1442, B2958

B1443

B2960, B3033

Ignition Key Resistor Signal

B1442, B2957

B1442, B2958

B1443, B2958

B2960, B3033

Circuit/System Description

The immobilizer system determines whether engine starting will be allowed based on a pull-down voltage created by the security resistor located in the ignition switch. When the ignition is in the START position, 5 volts is applied to the security resistor by the body control module (BCM) via the ignition key resistor signal circuit. A signal is provided back to the BCM by the off/run/crank voltage circuit. This circuit is also used in power moding operations. With the ignition in the START position, a voltage value is produced on ignition key resistor signal circuit based on the resistance of the security resistor. Each available resistor will produce a unique voltage value seen at the BCM. During immobilizer programming, the BCM learns this voltage value. On a start attempt, the BCM will compare actual voltage seen to the learned value. If the voltage seen and the learned value do not match, vehicle starting will be disabled.

Conditions for Running the DTC

The ignition is ON.

Conditions for Setting the DTC

B2957

The voltage value seen at the BCM on the ignition key resistor signal circuit is less than 0.4 volts for 1 second.

B2958

The voltage value seen at the BCM on the ignition key resistor signal circuit is greater than 4.8 volts for 1 second.

B2960

The voltage value seen at the BCM is valid, but does not match the stored value.

B3033

The voltage value seen at the BCM is invalid and indicates a tamper condition.

Action Taken When the DTC Sets
    • Vehicle starting will be disabled.
    • The security indicator is illuminated.

B3033

The BCM will enter the tamper state. Any attempt at starting will be ignored for a period of 10 minutes.

Conditions for Clearing the DTC
    • A current DTC will clear when the fault is no longer present.
    • A history DTC will clear after 100 concurrent malfunction free ignition cycles.

Reference Information

Schematic Reference

Immobilizer Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Immobilizer Description and Operation

Electrical Information Reference

    •  Circuit Testing
    •  Connector Repairs
    •  Testing for Intermittent Conditions and Poor Connections
    •  Wiring Repairs

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

B2960

Perform the 10 Minute Vehicle Key Relearn procedure. The BCM should successfully learn the voltage value and DTC should clear.

Circuit/System Testing
  1. Ignition OFF, disconnect the harness connector at the ignition switch.
  2. Ignition ON, test for 4.8-5.2 volts between the 5 V reference circuit terminal 5 and ground.
    3. ⇒If greater than the specified range, test the 5 V reference circuit for a short to voltage. If the circuit tests normal, replace the BCM.
    ⇒If less than the specified range, test the 5 V reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the BCM.
  3. Ignition OFF, connect the harness connector at the ignition switch. Disconnect the X2 harness connector at the BCM.
  4. Ignition in the CRANK position, test for 10Ω-18k Ω between the 5 V reference circuit terminal A42 and the signal circuit terminal A14.
    5. ⇒If greater than the specified range, test the signal circuit for an open/high resistance. If the circuit tests normal, test or replace the ignition switch.
    ⇒If less than the specified range, test or replace the ignition switch.
  5. Connect the X2 harness connector at the BCM.

    6. Important: Do not start the vehicle. Observe the parameter while momentarily placing the ignition switch in the CRANK position.

  6. Ignition in the CRANK position, verify the scan tool BCM Ign. Off/Run/Crank parameter is Active.
    7. ⇒If not the specified value, test the signal terminal A14 circuit for a short to ground. If the circuit tests normal, replace the BCM.
  7. If all circuits test normal, test or replace the ignition switch.

Component Test
  1. Ignition OFF, disconnect the harness connector at the ignition switch.
  2. With the switch in the OFF position, test for infinite resistance between the signal terminal 4 and the 5 V reference terminal 5.
    3. ⇒If less than the specified value, replace the ignition switch.
  3. With the switch in the RUN position, test for less than 10 Ω between the signal terminal 4 and the 5 V reference terminal 5.
    4. ⇒If greater than the specified range, replace the ignition switch.
  4. With the switch in the CRANK position, test for 10Ω-18k Ω between the signal terminal 4 and the 5 V reference terminal 5.
    5. ⇒If not within the specified range, replace the ignition switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Ignition and Start Switch Replacement
    •  Control Module References for BCM replacement, setup, and programming