Skip to content
Tahoe / Yukon Service Manual

DTC P0641, P0651, P0697, or P06A3

Engine Controls and Fuel - 3.0L LM2 Diesel | Diagnostic Information and Procedures | Document ID: 5590532 Diagnostic Instructions Perform the Diagnostic System Check prior to using this diagnostic procedure: Diagnostic System Check - Vehicle Review the description of Strategy Based Diagnosis: Strategy Based Diagnosis An overview of each diagnostic category can be found here: Diagnostic Procedure Instructions DTC Descriptor DTC P0641 Sensor Reference Circuit DTC P0651 Sensor Reference 2 Circuit DTC P0697 Sensor Reference 3 Circuit DTC P06A3 Sensor Reference 4 Circuit Diagnostic Fault Information

Circuit Short to Ground Open/High Resistance Short to Voltage Signal Performanc
Sensor Reference P0641 * — P0641 * —
Sensor Reference 2 P0651 * — P0651 * —
Sensor Reference 3 P0697 * — P0697 * —
Sensor Reference 4 P06A3 * — P06A3 * —
* Additional DTCs may set

Typical Scan Tool Data Sensor Reference

Circuit Short to Ground Open Short to Voltage
Operating Conditions: Ignition = On Parameter Normal Range: Okay
Sensor Reference Circuit Status Malfunction Okay Malfunction
Sensor Reference Circuit Status 2, 3, 4 Malfunction Okay Malfunction
Circuit Description
Sensor Reference Regulated voltage supplied by the control module.
Component Description
K20 Engine Control Module The control module contains a microprocessor used to process input data to control outputs. The control module controls a series of actuators to ensure optimal engine performance. The control module does this by reading values from a variety of sensors, interprets the data and adjusts the engine actuators accordingly.

The control module consists of 4 internal 5 V reference circuits. The 5 V reference circuit provides 5 V for one or more sensors. All sensors will be affected when a short to ground or voltage is on a shared 5 V reference circuit. Conditions for Running the DTC Ignition and Start Signal = Greater than 6.4 V Ignition and Start Switch Signal = On Frequency the DTC runs = Continuously — After the running conditions are met Conditions for Setting the DTC Condition 1 Sensor Reference = Less than 4.88 V Condition 2 Sensor Reference = Greater than 5.13 V Condition 3 The following parameters are not within 0.05 V of each other: Sensor Reference Sensor Reference 2, 3, 4 Actions Taken When the DTC Sets DTCs listed in the DTC Descriptor category = Type A DTC Conditions for Clearing the DTC DTCs listed in the DTC Descriptor category = Type A DTC Reference Information Schematic Reference Engine Controls Schematics Connector End View Reference Master Electrical Component List 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 Control Module References Circuit/System Verification

  1. Ignition » On / Vehicle » In Service Mode
  2. Verify the scan tool parameter: Sensor Reference Circuit Status = Okay Sensor Reference 2 Circuit Status = Okay Sensor Reference 3 Circuit Status = Okay Sensor Reference 4 Circuit Status = Okay ⇒ If not the specified state Refer to: Circuit/System Testing ⇓ If the specified state
  3. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data. Verify the DTC does not set. ⇒ If the DTC sets Refer to: Circuit/System Testing ⇓ If the DTC is not set
  4. All OK. Circuit/System Testing
  5. Ignition/Vehicle » Off
  1. Disconnect the electrical connector at one of the following components, depending on the DTC that is set: P0641 B23E Camshaft Position Sensor - Exhaust B65 Intake Manifold Pressure and Air Temperature Sensor Q14A Exhaust Gas Recirculation Valve 1 Q14B Exhaust Gas Recirculation Valve 2 M103 Turbocharger Vane Position Actuator M122 Exhaust Pressure Regulator Valve P0651 B1 A/C Refrigerant Pressure Sensor B22 Brake Pedal Position Sensor B26 Crankshaft Position Sensor B321 Crankcase Pressure Sensor B345P Exhaust Pressure Differential Sensor - Particulate Filter B345R Exhaust Pressure Differential Sensor - Exhaust Gas Recirculation B37B Engine Oil Pressure Sensor Q22 Intake Manifold Tuning Solenoid Valve Q38 Throttle Body Q74 Engine Coolant Bypass Valve Q97M Engine Coolant Flow Control Valve - Main P0697 B107 Accelerator Pedal Position Sensor 2 P06A3 B47B Fuel Rail Pressure Sensor B107 Accelerator Pedal Position Sensor 1
  2. Ignition » On / Vehicle » In Service Mode
  3. Verify the scan tool parameter: Sensor Reference Circuit Status = Malfunction — For the circuit that set the DTC. ⇒ If not the specified state after disconnecting a component from the circuit Test or replace the component: The component that was disconnected last. ⇒ If the specified state and there are components connected to the circuit Disconnect a component and repeat step 4. ⇓ If the specified state with all components disconnected from the circuit
  4. Test for 4.8 to 5.2 V between the test points: P0641 — Sensor Reference Circuit 5 V Reference circuit terminal 1 @ B23 Camshaft Position Sensor & Ground 5 V Reference circuit terminal 2 @ B65 Intake Manifold Pressure and Air Temperature Sensor & Ground 5 V Reference circuit terminal 1 @ Q14A Exhaust Gas Recirculation Valve 1 & Ground 5 V Reference circuit terminal 3 @ Q14B Exhaust Gas Recirculation Valve 2 & Ground 5 V Reference circuit terminal 4 @ M103 Turbocharger Vane Position Actuator & Ground 5 V Reference circuit terminal 3 @ M122 Exhaust Pressure Regulator Valve & Ground P0651 — Sensor Reference 2 Circuit 5 V Reference circuit terminal 1 @ B1 A/C Refrigerant Pressure Sensor & Ground 5 V Reference circuit terminal 6 @ B22 Brake Pedal Position Sensor & Ground 5 V Reference circuit terminal 1 @ B26 Crankshaft Position Sensor & Ground 5 V Reference circuit terminal 3 @ B37B Engine Oil Pressure Sensor & Ground 5 V Reference circuit terminal 1 @ B321 Crankcase Pressure Sensor & Ground 5 V Reference circuit terminal 1 @ B345P Exhaust Pressure Differential Sensor - Particulate Filter & Ground 5 V Reference circuit terminal 1 @ B345R Exhaust Pressure Differential Sensor - Exhaust Gas Recirculation & Ground 5 V Reference circuit terminal 3 @ Q22 Intake Manifold Tuning Solenoid Valve & Ground 5 V Reference circuit terminal 5 @ Q38 Throttle Body & Ground 5 V Reference circuit terminal 3 @ Q74 Engine Coolant Bypass Valve & Ground 5 V Reference circuit terminal 3 @ Q97M Engine Coolant Flow Control Valve - Main & Ground P0697 — Sensor Reference 3 Circuit 5 V Reference circuit terminal 6 @ B107 Accelerator Pedal Position Sensor — Sensor 2 & Ground P06A3 — Sensor Reference 4 Circuit 5 V Reference circuit terminal 1 @ B47B Fuel Rail Pressure Sensor & Ground 5 V Reference circuit terminal 1 @ B107 Accelerator Pedal Position Sensor — Sensor 1 & Ground ⇒ If less than 4.8 V 5.1. Ignition/Vehicle » Off 5.2. Disconnect the appropriate electrical connector: K20 Engine Control Module 5.3. Test for infinite resistance between the test points: P0641 5 V Reference circuit terminal 5 X2 @ Control module harness & Ground 5 V Reference circuit terminal 70 X1 @ Control module harness & Ground P0651 5 V Reference circuit terminal 7 X2 @ Control module harness & Ground 5 V Reference circuit terminal 48 X1 @ Control module harness & Ground P0697 5 V Reference circuit terminal 71 X1 @ Control module harness & Ground P06A3 5 V Reference circuit terminal 66 X2 @ Control module harness & Ground 5 V Reference circuit terminal 72 X1 @ Control module harness & Ground ⇒ If less than infinite resistance » Repair the short to ground on the circuit. ⇒ If infinite resistance » Replace the component: K20 Engine Control Module ⇒ If greater than 5.2 V 5.1. Ignition/Vehicle » Off 5.2. Disconnect the appropriate electrical connector: K20 Engine Control Module 5.3. Ignition » On / Vehicle » In Service Mode 5.4. Test for less than 1 V between the test points: P0641 5 V Reference circuit terminal 5 X2 @ Control module harness & Ground 5 V Reference circuit terminal 70 X1 @ Control module harness & Ground P0651 5 V Reference circuit terminal 7 X2 @ Control module harness & Ground 5 V Reference circuit terminal 48 X1 @ Control module harness & Ground P0697 5 V Reference circuit terminal 71 X1 @ Control module harness & Ground P06A3 5 V Reference circuit terminal 66 X2 @ Control module harness & Ground 5 V Reference circuit terminal 72 X1 @ Control module harness & Ground ⇒ If 1 V or greater » Repair the short to voltage on the circuit. ⇒ If less than 1 V » Replace the component: K20 Engine Control Module ⇓ If between 4.8 and 5.2 V
  5. All OK. Repair Instructions Perform the Diagnostic Repair Verification after completing the repair: Diagnostic Repair Verification Accelerator Pedal Replacement Air Conditioning Refrigerant Pressure Sensor Replacement Brake Pedal Position Sensor Replacement Camshaft Position Sensor Replacement Crankcase Pressure Sensor Replacement Crankshaft Position Sensor Replacement Engine Coolant Flow Control Valve Replacement — Q74 Engine Coolant Bypass Valve Engine Coolant Flow Control Valve Replacement — Q97M Engine Coolant Flow Control Valve - Main Engine Oil Pressure Sensor Replacement Exhaust Back Pressure Valve Replacement Exhaust Gas Recirculation Valve Replacement - Exhaust Gas Recirculation Cooler Exhaust Particulate Matter Sensor Replacement Exhaust Pressure Differential Sensor Bracket Replacement Fuel Pressure Sensor Replacement Intake Air Pressure and Temperature Sensor Replacement Throttle Body Assembly Replacement Compressor Air Intake Turbocharger Replacement For control module replacement, programming, and setup refer to: Control Module References