P1679 is a manufacturer-specific diagnostic trouble code, meaning its exact definition depends entirely on the vehicle make.
Because the code definition varies, the exact application must be verified before testing any components. The code alone does not prove that a specific module has failed.
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Key Takeaways
- P1679 is a manufacturer-specific code, and its definition varies significantly by vehicle make and model.
- On certain GM applications, it indicates an immobilizer environment identification failure, meaning the theft deterrent system cannot verify the vehicle’s identity.
- On specific Volkswagen and Audi applications, it points to a drive-by-wire or electronic throttle control circuit malfunction.
- On some Honda hybrid applications, it signifies a rotational speed control device (RSCD) signal circuit issue.
- Diagnosis requires verifying the exact factory definition for your vehicle before testing any circuits or replacing modules.
P1679 Code Description and Implications
P1679 is a manufacturer-specific powertrain code, and its exact definition depends on the vehicle application.
Certain GM applications (Chevrolet, Buick, etc.): P1679 indicates an “Immobilizer Environment Identification Failed” condition.
The powertrain control module and the immobilizer system cannot properly authenticate the vehicle’s identity or security environment, preventing the engine from starting.
Specific Volkswagen and Audi applications: P1679 signifies a “Drive-By-Wire MIL Circuit Open” or electronic throttle control range/performance problem.
The control module detects an open circuit or performance fault in the electronic throttle actuator or its malfunction indicator circuit.
Some Honda and Acura hybrid applications: P1679 points to a “RSCD Signal Circuit Malfunction.”
This relates to the rotational speed control device or integrated motor assist system signal circuit failing to operate within expected parameters.
Common Causes of the P1679 Code
Because the code definition varies, the causes depend entirely on the verified system.
For GM immobilizer applications, installing an unprogrammed or incorrect powertrain control module is one possible cause.
A faulty immobilizer module, damaged wiring between the theft deterrent module and the PCM, or a failed transponder key can also trigger this code.
For VW and Audi electronic throttle applications, a failed throttle body actuator motor or an open circuit in the throttle pedal sensor wiring is a possible cause.
Corroded connectors or poor grounds in the drive-by-wire harness can also disrupt the signal.
For Honda hybrid applications, causes may include a faulty IMA motor speed sensor, damaged high-voltage wiring, or internal hybrid control module faults.
Symptoms Associated With P1679
Symptoms vary widely based on the affected system and the exact vehicle application.
On GM applications with an immobilizer failure, the primary symptom is a no-start condition where the engine cranks but will not fire.
The security or theft deterrent light may flash or remain illuminated on the dashboard.
On VW and Audi applications, symptoms may include an illuminated check engine light, reduced engine power, or the vehicle entering a limp-home mode.
The electronic throttle may become unresponsive, causing severe drivability issues.
On Honda hybrid applications, symptoms may include the IMA system disabling, reduced fuel economy, or an illuminated check engine light.
Diagnosing the P1679 Trouble Code
Diagnosis must begin by confirming the exact factory definition for your specific make, model, and engine.
For GM immobilizer applications, technicians use a specialized scan tool to verify the VIN programmed in the PCM matches the immobilizer module.
They also inspect the communication circuits between the theft deterrent module and the powertrain control module.
For VW and Audi throttle applications, diagnosis involves testing the electronic throttle body motor resistance and checking the accelerator pedal position sensor circuits for opens or shorts.
For Honda hybrid applications, specialized hybrid system diagnostic routines are required to test the RSCD signal circuits safely.
Repairing the P1679 Issue
Repairs must follow confirmed diagnosis and vary significantly by implementation.
If the PCM and immobilizer module are mismatched on a GM application, reprogramming or replacing the confirmed failed module with the correct VIN data is necessary.
Wiring repairs must be completed if harness damage or corrosion is found in the security system circuits.
If the electronic throttle body fails testing on a VW or Audi application, replacing the throttle body assembly and performing the required adaptation is required.
Always verify the repair by clearing the codes and performing a test drive or key cycle to ensure the trouble code does not return.
Cost Considerations for P1679 Repairs
Repair costs depend heavily on the underlying fault and the specific vehicle application.
Addressing a wiring issue or a poor connection is less expensive, primarily involving diagnostic time and minor materials.
Reprogramming an immobilizer module or PCM involves moderate labor costs for specialized software access.
Conversely, replacing an electronic throttle body assembly or hybrid system components can be a more significant investment.
Costs will also vary based on diagnostic time, component accessibility, and local labor rates.
Prevention Strategies for Future Occurrences
Prevention strategies are tied to the specific failure mechanism of the affected system.
For immobilizer issues, ensuring that any replacement powertrain or security modules are properly programmed to the vehicle’s exact VIN helps prevent authentication failures.
Keeping electrical connectors clean and protected from moisture intrusion may reduce the risk of intermittent circuit faults in throttle or hybrid systems.
Some internal module or sensor failures occur without warning and cannot be reliably prevented through routine maintenance.
Troubleshooting Tips and Best Practices
Always verify the exact manufacturer definition for P1679 before purchasing parts or beginning repairs.
Do not assume an immobilizer module has failed solely based on the code without verifying the PCM programming and VIN data.
When diagnosing electronic throttle systems, avoid manually forcing the throttle plate open, as this can damage the internal actuator gears.
Consult the exact manufacturer service information for your specific vehicle to ensure accurate diagnostic routines and specifications.
More OBD-II Codes
| P1678 | P1677 | P1676 | P1675 |
| P1674 | P1673 | P1680 | P1681 |
| P1682 | P1683 | P1684 | P1685 |
| P1629 | P1631 | P1632 | P1641 |
| P0505 | P0638 | P1650 | P1660 |
| P1635 | P1638 | P1639 | P1651 |
Frequently Asked Questions
Is P1679 a generic OBD-II code?
No. P1679 is a manufacturer-specific code, meaning its exact definition depends entirely on the vehicle make. It can indicate an immobilizer failure, an electronic throttle circuit fault, or a hybrid system issue.
Can a P1679 code prevent my car from starting?
Yes, on certain GM applications, P1679 indicates an immobilizer environment identification failure. If the theft deterrent system cannot verify the vehicle’s identity, the engine will crank but will not start.
Will disconnecting the battery clear a P1679 code?
Disconnecting the battery may temporarily clear the code, but it does not repair the underlying module mismatch or circuit fault. The code will likely return, and battery disconnection can erase valuable diagnostic data.
Does P1679 always mean the immobilizer module is bad?
No. While it indicates an authentication failure on some applications, installing an incorrect or unprogrammed powertrain control module can trigger the code. The module should only be replaced after verifying VIN programming and circuit integrity.
Can I drive my vehicle with a P1679 code?
Driving advice depends on the application. If the code relates to an electronic throttle or immobilizer failure, the vehicle may not start or could enter a severe limp mode, making it unsafe or impossible to drive.
What Should You Do About the P1679 Code?
Confirm the exact factory definition for your specific vehicle before attempting any repairs.
Because P1679 is manufacturer-specific, testing the wrong system will waste time and money.
Follow the applicable manufacturer diagnostic procedure to inspect the relevant system and components, then repair or replace the confirmed failed part.
