P1682 Code? Here’s How to Fix It Quickly and Easily

P1682 is a manufacturer-specific OBD-II code indicating a voltage discrepancy in the ignition switch circuits supplying the engine control module. This definition primarily applies to General Motors and Saab vehicles.

Because this code monitors redundant power feeds, it does not automatically prove the ignition switch has failed. Wiring issues, blown fuses, or poor connections must be tested and ruled out first.

Key Takeaways

• P1682 indicates the engine control module detected a voltage difference between its two primary ignition power feed circuits.
• Possible causes include a failing ignition switch, blown fuses, corroded connectors, or damaged wiring harnesses.
• Symptoms often include a no-start condition, engine stalling, or an illuminated Check Engine Light.
• Diagnosis requires measuring the voltage at the module connectors and tracing the ignition feed circuits back to the switch.

P1682 Code Description and Implications

The P1682 code is defined as “Ignition 1 Switch Circuit 2.” It is a manufacturer-specific code primarily found on General Motors and Saab applications.

The engine control module receives ignition voltage through two separate circuits to verify the ignition switch position and ensure redundant power.

If the module detects a voltage difference between these two circuits that exceeds the manufacturer threshold, it stores the P1682 code.

Common Causes of the P1682 Code

• A failing or worn ignition switch that no longer supplies equal voltage to both output circuits.
• A blown fuse or faulty relay in one of the ignition feed circuits.
• Corroded, loose, or damaged connectors at the ignition switch, fuse block, or engine control module.
• Chafed, broken, or shorted wiring in the harness between the ignition switch and the engine control module.

Symptoms Associated With P1682

• Illuminated Check Engine Light.
• Engine cranks but will not start, as the module may disable fuel or spark if it cannot verify the ignition state.
• Engine stalling while driving if the ignition circuit intermittently loses voltage.
• Reduced electrical power or accessory malfunctions tied to the ignition switch.

Diagnosing the P1682 Trouble Code

Diagnosis must begin by checking for other related OBD2 Codes and verifying the battery voltage and charging system health.

Inspect the fuses and relays associated with the engine control module and ignition switch circuits.

Use a multimeter to measure the voltage at the specific ignition feed pins on the engine control module connector while the key is in the Run position.

If a voltage discrepancy is confirmed, trace the affected circuit back through the fuse block and ignition switch to locate the point of resistance or failure.

Repairing the P1682 Issue

Repairs must follow confirmed diagnosis. Do not replace components based on the code description alone.

If a blown fuse is found, replace it and investigate the cause of the overload.

If the wiring or connectors are damaged or corroded, repair or replace the affected harness sections and terminals.

If the ignition switch fails electrical testing or shows internal resistance on one circuit, replace the switch assembly with a component meeting the correct vehicle specification.

Cost Considerations for P1682 Repairs

Cost depends on diagnostic time, component accessibility, required parts, and labor.

Replacing a fuse or repairing a localized wiring issue involves minimal parts and labor expenses.

Replacing an ignition switch or addressing deep harness damage requires moderate to significant labor costs. Exact pricing varies by vehicle model and region.

Prevention Strategies for Future Occurrences

• Keep the ignition switch and surrounding electrical connections clean and free from moisture intrusion.
• Avoid overloading accessory circuits tied to the ignition switch, which can cause premature internal contact wear.
• Address any intermittent starting or stalling issues immediately before they lead to complete circuit failure.

Troubleshooting Tips and Best Practices

• Do not replace the engine control module based solely on a P1682 code. The fault almost always lies in the external power feed circuits or the ignition switch.
• Consult the exact factory wiring diagram for your specific vehicle, as the pinouts and circuit routing for the ignition feeds vary significantly between platforms.
• Check for applicable technical service bulletins or recall campaigns, as certain vehicles had widespread ignition switch recalls that directly relate to this code.

More OBD-II Codes

Frequently Asked Questions

Is P1682 a generic or manufacturer-specific code?

No. P1682 is a manufacturer-specific code. Its definition regarding an ignition switch circuit voltage discrepancy primarily applies to General Motors and Saab vehicles.

Will a P1682 code prevent my car from starting?

Yes. If the engine control module cannot verify the ignition switch position due to the voltage discrepancy, it may disable the fuel injectors, resulting in a no-start condition.

Can a bad battery cause a P1682 code?

A severely depleted battery usually sets different codes, but poor battery terminal connections can cause systemic voltage drops that might trigger a discrepancy between the ignition feed circuits.

Is there a recall for the P1682 code?

Certain General Motors vehicles had major recalls for faulty ignition switches that could cause stalling and set codes like P1682. Check your VIN with the manufacturer to verify open recalls.

Can I drive my car with a P1682 code?

It is not recommended. If the engine stalls unexpectedly due to an intermittent ignition circuit failure, you could lose power steering and braking assist, creating a severe safety hazard.

What Should You Do About the P1682 Code?

Confirm the exact factory wiring diagram for your vehicle, then follow the applicable manufacturer diagnostic procedure. Measure the voltage at the engine control module connectors and trace the relevant system and components to identify the root cause, verify the repair, and then clear the codes.