The P1671 diagnostic trouble code is a manufacturer-specific powertrain code. Its exact definition depends heavily on the vehicle make, pointing to an internal control module driver fault, a camshaft actuator issue, or a relay circuit malfunction.
Because this code targets entirely different systems across manufacturers, the exact vehicle application must be verified before diagnosis. The code alone does not prove a specific component has failed without proper testing.
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Key Takeaways
- P1671 is a manufacturer-specific powertrain code with differing definitions depending on the vehicle make.
- On GM and Chevrolet applications, it indicates a Quad Driver Module ‘C’ or Driver 4 Line 1 fault within the ECM.
- On Volvo applications, it points to a Camshaft Position (CMP) Actuator Performance or Variable Valve Timing (VVT) fault.
- On Saab and VAG applications, it indicates a relay control circuit malfunction, such as the throttle limp-home or fuel pump relay.
- Diagnosis requires verifying the exact factory definition and testing the relevant internal driver, actuator, or relay circuit.
P1671 Code Description and Implications
The P1671 code indicates that a control module has detected a specific fault within the engine management, valve timing, or relay systems. Because it is a manufacturer-specific code, the exact monitored component varies significantly by brand.
Some GM and Chevrolet applications: P1671 indicates a Quad Driver Module ‘C’ or Driver 4 Line 1 fault. The Engine Control Module (ECM) uses internal output drivers to provide ground paths for various relays and solenoids. A fault here means the ECM detects an internal circuit failure or an external short on a controlled component.
Certain Volvo applications: The code indicates a Camshaft Position (CMP) Actuator Performance Problem or Signal Out of Range. The ECM detects that the Variable Valve Timing (VVT) solenoid or camshaft actuator is not responding correctly or is out of the expected mechanical range.
Some Saab and VAG applications: P1671 indicates a relay control circuit fault, such as a Throttle Actuator Limp Home Relay short to positive or a Fuel Pump Relay circuit malfunction.
Common Causes of the P1671 Code
Because P1671 applies to different systems across different brands, the root cause depends on the verified vehicle application.
GM and Chevrolet Causes: A short to ground or voltage in the wiring harness of a component controlled by Driver 4, such as the cooling fan or EVAP purge solenoid, which can damage the internal ECM driver.
Volvo Causes: A failing VVT solenoid, clogged oil control passages, a stretched timing belt, or a faulty camshaft position sensor preventing proper valve timing adjustment.
Saab and VAG Causes: A failing relay, damaged wiring harness, poor electrical connections, or a short to positive voltage in the specific relay control circuit.
Symptoms Associated With P1671
When the control module detects a critical system fault, it illuminates a warning light and may alter vehicle operation.
Warning Lights: The Check Engine Light will illuminate. On some applications, a reduced power or limp mode warning may also appear on the instrument cluster.
Drivability: On GM applications, malfunctioning accessories like the cooling fan may occur. On Volvo applications, rough idling, engine misfires, and poor acceleration are likely. On relay circuit applications, the vehicle may experience a no-start condition or fuel delivery issues.
Diagnosing the P1671 Trouble Code
Accurate diagnosis begins by verifying the exact vehicle application and reviewing manufacturer-specific service information.
For GM and Chevrolet applications: Identify which specific components are controlled by Driver 4 Line 1 using the manufacturer wiring diagram. Inspect the wiring and connectors for those components to find a short that may have damaged the internal ECM driver.
For Volvo applications: Inspect the VVT solenoid and its wiring. Verify engine oil level and condition, as low oil pressure can prevent the camshaft actuator from operating correctly. Check the timing belt alignment.
For Saab and VAG applications: Test the specific relay and its control circuit for opens, shorts, or excessive resistance according to the manufacturer procedure.
Repairing the P1671 Issue
Repairs must follow the confirmed root cause identified during diagnosis.
ECM and Wiring Repairs: If an external short is found on GM applications, repair the harness and test the ECM. If the internal driver is confirmed failed, the ECM requires replacement and programming.
Actuator and Timing Repairs: If the VVT solenoid fails testing or oil passages are clogged on Volvo applications, clean or replace the affected components. If the timing is off, perform the necessary mechanical timing corrections.
Relay Circuit Repairs: If the relay or wiring fails electrical testing on Saab or VAG applications, replace the confirmed failed component and clear the codes.
Cost Considerations for P1671 Repairs
Cost depends on diagnostic time, component accessibility, required parts, programming requirements, and labor.
Replacing a VVT solenoid or a standard relay involves moderate labor. However, replacing and programming an ECM due to an internal quad driver failure requires significant diagnostic time and specialized dealer-level equipment.
Prevention Strategies for Future Occurrences
Maintaining the correct engine oil level and performing regular oil changes helps ensure the Variable Valve Timing actuators receive adequate oil pressure on Volvo applications.
Inspecting exposed wiring harnesses near relays and engine accessories helps prevent shorts that can damage internal ECM drivers on GM applications.
Troubleshooting Tips and Best Practices
Follow these practices to avoid misdiagnosis and ensure accurate repairs.
Do not assume the ECM has failed just because a Quad Driver Module code is present: An external short to ground in a controlled component’s wiring is a frequent cause of internal driver damage. Always verify the external wiring harness first.
Check for related codes: Look for accompanying camshaft position or specific relay circuit codes, which might help pinpoint the exact component causing the driver or circuit fault.
Verify your definition: Always confirm whether your specific vehicle uses the ECM driver, camshaft actuator, or relay circuit definition before ordering parts.
More OBD-II Codes
| P1651 | P1652 | P1653 | P1654 |
| P1655 | P1660 | P1672 | P1673 |
| P1674 | P1675 | P1676 | P1677 |
| P0601 | P0603 | P0604 | P0605 |
| P1678 | P1679 | P1680 | P1681 |
| P1682 | P1683 | P1684 | P1685 |
Frequently Asked Questions
Is P1671 a generic or manufacturer-specific code?
No. P1671 is a manufacturer-specific powertrain code. Its definition varies significantly by brand, indicating an ECM internal driver fault, a camshaft actuator issue, or a relay circuit malfunction.
Can I drive my vehicle with a P1671 code?
The vehicle may remain drivable, but a VVT fault can cause severe engine misfires, and an ECM driver fault can disable critical cooling fans. Driving should be limited until repaired.
Will disconnecting the battery clear the P1671 code?
Disconnecting the battery might temporarily clear the code. However, it does not repair the underlying shorted wire, failed VVT solenoid, or damaged ECM driver, and the code will return.
Can low oil cause a P1671 code?
Yes. On Volvo applications where P1671 indicates a camshaft actuator performance fault, low engine oil level or poor oil pressure can prevent the VVT system from operating correctly, triggering the code.
Does P1671 affect the transmission?
No. The P1671 code relates strictly to the engine control module drivers, variable valve timing, or specific engine relays. It does not directly affect the automatic or manual transmission operation.
What Should You Do About the P1671 Code?
When a P1671 code appears, confirm the exact factory definition for your specific vehicle make and model. Because this code targets entirely different engine management, valve timing, and relay systems depending on the manufacturer, applying the wrong diagnostic path will lead to misdiagnosis.
Follow the applicable manufacturer diagnostic procedure to test the relevant system and components. Once the root cause is confirmed, complete the necessary electrical repairs, mechanical timing corrections, or module replacements before returning the vehicle to normal service.
