GM Service Manual Online
For 1990-2009 cars only

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 Descriptor

DTC B2850 01: Telescope Forward Switch Circuit Short to Battery

DTC B2855 01: Telescope Rearward Switch Circuit Short to Battery

DTC B2870 01: Tilt Up Switch Circuit Short to Battery

DTC B2875 01: Tilt Down Switch Circuit Short to Battery

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Steering Wheel Column Tilt Telescope Switch B+

1, 2

1, 2

--

--

Steering Column Tilt Up Switch Signal

1

1

B2870 01

--

Steering Column Tilt Down Switch Signal

1

1

B2875 01

--

Steering Column Telescope Reverse Switch Signal

2

2

B2855 01

--

Steering Column Telescope Forward Switch Signal

2

2

B2850 01

--

1. Tilt Malfunction

2. Telescope Malfunction

Circuit Description

The memory seat module (MSM) receives voltage inputs from the tilt/telescope switch based on the position of the switch. The MSM then supplies battery voltage and a ground to the tilt or telescope motor control circuits depending on which direction of movement is requested.

Conditions for Running the DTC

The ignition ON.

Conditions for Setting the DTC

The MSM detects a tilt or telescope switch input for more than 30 consecutive seconds after the tilt or telescope motor movement has stopped.

Action Taken When the DTC Sets

    • The tilt or telescope motor will be deactivated.
    • Memory recall functions will be disabled.

Conditions for Clearing the DTC

    • A current DTC will clear when the failed switch input is no longer active.
    • A history DTC will clear after 100 ignition cycles.

Diagnostic Aids

An intermittently stuck tilt or telescope switch may cause a DTC to set.

Reference Information

Schematic Reference

Tilt/Telescoping Steering Column Schematics

Connector End View Reference

Component Connector End Views

Description and Operation

Steering Wheel and Column 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

Ignition ON, view the appropriate scan tool Tilt or Telescope Switch parameter while cycling the appropriate switch between states.The parameter should change between Active and Inactive.

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the tilt/telescope switch.
  2. Ignition ON, verify a test lamp illuminates between terminal 4 and ground.
  3. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance.
  4. Verify with the scan tool that the appropriate switch parameter is Inactive.
  5. If not the specified value, test the appropriate signal circuit for a short to voltage. If the circuit tests normal, replace the MSM.
  6. Install a 3A fused jumper wire between the appropriate circuit terminal 1, 2, 3, or 5 and terminal 4. Verify with the scan tool that the appropriate switch parameter is Active.
  7. If not the specified value, test the signal circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the MSM.
  8. If all circuit test normal, test or replace the tilt/telescope switch.

Component Testing

Tilt/Telescope Switch

  1. Ignition OFF, disconnect the harness connector at the tilt/telescope switch.
  2. Test for infinite resistance between terminals 1, 2, 3, and 5 with the switch in the neutral position:
  3. If less than the specified range, replace the tilt/telescope switch.
  4. Test for less than 1 ohm between terminal 4 and terminals 1, 2, 3, and 5 with the switch in each appropriate position.
  5. If greater than the specified value, replace the tilt/telescope switch.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Steering Column Replacement
    •  Control Module References for MSM replacement, setup, and programming