GM Service Manual Online
For 1990-2009 cars only

Diagnostic Instructions

    • Perform the Diagnostic System Check - Vehicle prior to using the 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 B0560: Tachometer Circuit

Diagnostic Fault Information

Circuit

Short to Ground

Open/High Resistance

Short to Voltage

Signal Performance

Engine Speed Signal Circuit

B0560

B0560

B0560

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Circuit Description

The instrument panel cluster (IPC) receives the engine speed information from the engine control module (ECM)/powertrain control module (PCM) through the engine speed signal circuit. The ECM/PCM converts the data from the engine speed sensor to a 2 pulses/(engine revolution) signal. The ECM/PCM also sends a class 2 message to the IPC indicating the engine speed. If the IPC determines there is a loss of the engine speed signal from the ECM/PCM due to a engine speed signal circuit malfunction, a DTC sets.

Conditions for Running the DTC

    • The engine speed is greater than 800 RPM.
    • The ignition voltage is greater than 9 volts, but less than 18 volts.

Conditions for Setting the DTC

    • The IPC detects that the engine speed signal circuit does not match the engine speed from the class 2 serial data circuit.
    • The above condition is present for at least 5 seconds.

Action Taken When the DTC Sets

The IPC stores the DTC in memory.

Conditions for Clearing the DTC

    • A last test failed (current DTC) clears when the diagnostic runs and does not fail.
    • A history DTC clears after 100 consecutive malfunction-free warm-up cycles.
    • The IPC receives the clear code command from the scan tool.

Reference Information

Schematic Reference

    •  Instrument Cluster Schematics
    •  Engine Controls Schematics for the 4.2L engine
    •  Engine Controls Schematics for the 5.3L engine
    •  Engine Controls Schematics for the 6.0L engine

Connector End View Reference

    •  Displays and Gages Connector End Views
    •  Powertrain Control Module Connector End Views
    •  Engine Control Module Connector End Views for the 5.3L engine
    •  Engine Control Module Connector End Views for the 6.0L engine

Electrical Information Reference

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

Scan Tool Reference

Scan Tool Data List

Circuit/System Testing

  1. Ignition OFF, disconnect the harness connector at the ECM/PCM. Install a signal generator and instrument panel tester between the engine speed signal circuit and ground.
  2. Ignition ON, set the signal generator to generate a tachometer signal. Verify that the tachometer indicates a RPM reading.
  3. If no RPM reading is present, test the signal circuit for an open/high resistance, a short to voltage, or a short to ground. If the circuit tests normal, replace the IPC.
  4. If all circuits test normal, test or replace the ECM/PCM.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

Control Module References for the ECM/PCM and IPC replacement, setup, and programming