GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2006 🢒 Epica 🢒 Vehicle Control Systems 🢒 Vehicle DTC Information 🢒 DTC P0642, P0643, P0698, or P0699

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 provide an overview of each diagnostic category.

DTC Descriptors

DTC P0642: 5-Volt Reference 1 Circuit Low Voltage

DTC P0643: 5-Volt Reference 1 Circuit High Voltage

DTC P0698: 5-Volt Reference 3 Circuit Low Voltage

DTC P0699: 5-Volt Reference 3 Circuit High Voltage

Circuit/System Description

The engine control module (ECM) has several 5-volt reference circuits. The ECM provides the 5-volt reference to various sensors. Each reference circuit provides a 5-volt reference for greater than one sensor. A short to ground or voltage on one of the 5-volt reference circuits will affect all components connected to that 5-volt reference circuit. The ECM monitors the voltage on the 5-Volt Reference 1 and 5-Volt Reference 3 circuits.

Conditions for Running the DTC
    • The ignition is ON.
    • The DTCs run continuously when the above condition is met.

Conditions for Setting the DTC

The control module detects a voltage greater than 5.2 volts, or less than 4.8 volts, on either 5-volt reference circuit for greater than 1 second.

Action Taken When the DTC Sets
    • DTCs P0642 and P0643 are Type B DTCs.
    • DTCs  P0698 and P0699 are Type A DTCs.

Conditions for Clearing the DTC
    • DTCs P0642 and P0643 are Type B DTCs.
    • DTCs  P0698 and P0699 are Type A DTCs.

Diagnostic Aids

Important: An internal ECM 5-volt regulator supplies 5 volts to the 5-volt reference circuits and the fuel level sensor signal circuit. When an external 5-volt reference 1 circuit is shorted, DTC P0462 or P0463 sets even though there is no condition with the fuel level sensor.

P0642 and P0643

The 5-volt reference 1 circuit provides 5 volts to the following sensors:

    • The manifold absolute pressure (MAP) sensor
    • The exhaust gas recirculation (EGR) valve position sensor
    • The intake manifold tuning (IMT) valve position sensor
    • The fuel tank pressure (FTP) sensor

P0698 and P0699

The 5-volt reference 3 circuit provides 5 volts to the following sensors:

    • The accelerator pedal position (APP) sensor 1
    • The accelerator pedal position (APP) sensor 2
    • The throttle position (TP) sensor 1
    • The throttle position (TP) sensor 2

Reference Information

Schematic Reference

Engine Controls Schematics

Connector End View Reference

    •  Engine Control Module Connector End Views
    •  Engine Controls Connector End Views

Electrical Information Reference

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

    •  Scan Tool Data List
    •  Scan Tool Data Definitions
    •  Scan Tool Output Controls

Circuit/System Verification
  1. Ignition ON, observe the DTC information with a scan tool. DTCs P0642, P0643, P0698, and P0699 should not set.
  2. If the vehicle passes the Circuit/System Verification test, then operate the vehicle within the conditions for running the DTC. You may also operate the vehicle within the conditions that are captured in the Freeze Frame/Failure Records Data List.

Circuit/System Testing

    Important: Additional DTCs will set when disconnecting the components.

  1. Ignition OFF, disconnect the harness connector at all appropriate sensors for the applicable DTC. Refer to Diagnostic Aids.
  2. Ignition ON, test for 4.8-5.2 volts between one of the applicable 5-volt reference circuits and ground.
    3. ⇒If less than the specified range, test for a short to ground on all the applicable 5-volt reference circuits. If all circuits test normal, replace the control module.
    ⇒If greater than the specified range, test for a short to voltage on all the applicable 5-volt reference and signal circuits. If all circuits test normal, replace the control module.

    Important: A short to voltage on the signal circuit of certain components may cause this DTC to set.

  3. Connect each component associated with the 5-volt reference circuit one at a time while monitoring the voltage. The voltage should not change greater than 0.5 volt.
    4. ⇒ If the voltage display increases more than the specified value when a component is connected, test the signal circuit for a short to voltage. If all circuits test normal, replace the control module.
    ⇒ If the voltage display decreases more than the specified value when a component is connected, replace the component.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

    •  Accelerator Pedal Position Sensor Replacement
    •  Exhaust Gas Recirculation Valve Replacement
    •  Manifold Absolute Pressure Sensor Replacement
    •  Throttle Body Assembly Replacement
    •  Intake Manifold Tuning Valve Actuator Replacement
    •  Control Module References for ECM replacement, setup, and programming