The P1682 diagnostic trouble code (DTC) is a manufacturer-specific code related to the ignition system, particularly the ignition switch circuit. This code is commonly found in General Motors (GM) vehicles and indicates a discrepancy in voltage between two ignition circuits monitored by the Powertrain Control Module (PCM).
| P1682 Code Meaning | P1682 Code Common Causes |
|---|---|
| Ignition 1 Switch Circuit 2 Malfunction | Faulty ignition switch |
| Voltage difference detected between ignition feeds | Damaged or corroded wiring in the ignition circuit |
| ECM detects inconsistent ignition voltage signals | Blown fuses or faulty relays |
| Driver 5 Line 2 issue (GM-specific) | Malfunctioning Powertrain Control Module (PCM) |
Faulty Ignition Switch
The ignition switch is a crucial component in your vehicle’s electrical system, controlling power distribution to various systems including the engine and accessories. When it malfunctions, it can lead to the P1682 code.
Symptoms
- Difficulty starting the vehicle
- Intermittent stalling
- Electrical system behaving erratically
- Dashboard warning lights flickering or illuminating unexpectedly
Technical Explanation
The ignition switch in modern vehicles is connected to the PCM and provides two separate voltage signals. The first signal (Ignition 1) is a constant voltage that maintains the PCM’s memory even when the key is off. The second signal (Ignition 2) provides voltage when the key is turned to the “on” position. The P1682 code is triggered when the PCM detects a discrepancy between these two voltage signals.
Step-by-Step Diagnosis
- Connect an OBD-II scanner to verify the P1682 code.
- Check the battery voltage to ensure it’s above 12.6 volts.
- Inspect the ignition switch visually for any signs of damage or wear.
- Use a multimeter to test the voltage at the ignition switch terminals in different key positions.
- Compare the voltage readings with the specifications in your vehicle’s service manual.
Solution Methods
- Clean the ignition switch contacts if corrosion is present.
- If cleaning doesn’t resolve the issue, replace the ignition switch.
- For vehicles with a separate ignition switch and lock cylinder, you may only need to replace the electrical portion.
Cost Estimate
- DIY Repair: $50 – $150 for parts
- Professional Repair: $200 – $400, including labor
Warnings and Recommendations
Warning: Disconnecting the battery may reset your vehicle’s computer systems. Be prepared to reset radio presets, clock, and other personalized settings.
Always consult your vehicle’s specific repair manual before attempting any repairs. If you’re uncomfortable working with electrical systems, it’s best to seek professional assistance.
Damaged or Corroded Wiring in the Ignition Circuit
Wiring issues are another common cause of the P1682 code. Over time, wires can become damaged, corroded, or loose, leading to inconsistent voltage signals.
Symptoms
- Intermittent electrical issues
- Engine misfires or stalling
- Difficulty starting the vehicle
- Multiple electrical system malfunctions
Technical Explanation
The ignition circuit consists of various wires connecting the ignition switch to the PCM and other components. Any break, short, or high resistance in these wires can cause voltage discrepancies that trigger the P1682 code.
Step-by-Step Diagnosis
- Visually inspect all accessible wiring in the ignition circuit.
- Check for signs of damage, corrosion, or loose connections.
- Use a multimeter to perform continuity tests on suspected wires.
- Check voltage drop across connections to identify high-resistance points.
- Consult your vehicle’s wiring diagram to trace the ignition circuit completely.
Solution Methods
- Clean corroded connections using electrical contact cleaner.
- Repair or replace damaged wires.
- Secure loose connections and replace faulty connectors.
- In severe cases, you may need to replace entire wiring harnesses.
Cost Estimate
- DIY Repair: $20 – $100 for materials
- Professional Repair: $200 – $600, depending on the extent of wiring damage
Warnings and Recommendations
Caution: Incorrect wiring repairs can lead to short circuits and potential electrical fires. If you’re unsure about your ability to safely repair wiring, consult a professional.
Always use the correct gauge wire and proper connectors when making repairs. Heat shrink tubing can provide additional protection for repaired wires.
Blown Fuses or Faulty Relays
Fuses and relays play a crucial role in protecting and controlling the ignition system. When they fail, it can lead to voltage inconsistencies and trigger the P1682 code.
Symptoms
- Vehicle won’t start
- Certain electrical systems not functioning
- Intermittent electrical issues
- Clicking sound when trying to start the vehicle (in case of a faulty relay)
Technical Explanation
Fuses are designed to break the circuit when excessive current flows, protecting other components from damage. Relays are electromagnetic switches that control high-current circuits with low-current signals. If either of these components fails, it can disrupt the proper functioning of the ignition system.
Step-by-Step Diagnosis
- Locate the fuse box (usually under the dashboard or in the engine compartment).
- Check the fuse diagram to identify ignition-related fuses.
- Visually inspect fuses for signs of burning or a broken metal strip.
- Use a multimeter or fuse tester to check for continuity in suspected fuses.
- Locate and inspect ignition-related relays.
- Test relay function using a multimeter or by swapping with a known good relay.
Solution Methods
- Replace any blown fuses with ones of the correct amperage.
- Replace faulty relays.
- If fuses or relays blow repeatedly, investigate the underlying cause of the excessive current draw.
Cost Estimate
- DIY Repair: $5 – $50 for fuses and relays
- Professional Repair: $50 – $200, including diagnostic time
Warnings and Recommendations
Never replace a blown fuse with one of a higher amperage rating. This can lead to electrical fires or damage to other components.
Keep a set of spare fuses in your vehicle for emergencies. If a fuse blows repeatedly, there’s likely an underlying issue that needs to be addressed by a professional.
Malfunctioning Powertrain Control Module (PCM)
While less common, a faulty PCM can cause the P1682 code. The PCM is responsible for monitoring and controlling various engine and transmission functions, including the ignition system.
Symptoms
- Multiple error codes present
- Erratic engine performance
- Transmission shifting issues
- Various electrical system malfunctions
Technical Explanation
The PCM uses input from various sensors to control engine operation. If the PCM itself is malfunctioning, it may misinterpret the ignition switch signals or fail to properly control the ignition system, leading to the P1682 code.
Step-by-Step Diagnosis
- Scan for additional error codes that might indicate a PCM issue.
- Check the PCM’s power and ground connections.
- Inspect the PCM for signs of physical damage or water intrusion.
- Perform a voltage drop test on PCM power and ground circuits.
- Consider having the PCM bench tested by a specialist.
Solution Methods
- Repair any damaged connections or wiring to the PCM.
- Update the PCM software if available.
- In cases of severe damage, replace the PCM.
- After replacement or repair, perform necessary relearn procedures.
Cost Estimate
- DIY Repair: Not recommended for PCM replacement
- Professional Repair: $500 – $2000, depending on the vehicle and whether replacement is necessary
Warnings and Recommendations
Replacing or reprogramming a PCM is a complex task that usually requires specialized equipment. It’s best left to professionals to avoid potentially costly mistakes.
Before concluding that the PCM is at fault, exhaust all other possible causes of the P1682 code. PCM failure is relatively rare compared to other causes.
Frequently Asked Questions About P1682
- Can I drive my car with a P1682 code?
While the vehicle may still run, it’s not recommended to drive with this code present. The ignition system issues could lead to stalling or other dangerous situations while driving. - How urgent is it to fix a P1682 code?
This code should be addressed as soon as possible. Ignition system problems can worsen quickly and potentially leave you stranded or cause more extensive damage. - Will a P1682 code clear itself?
It’s unlikely that this code will clear on its own. The underlying issue needs to be resolved before the code will clear permanently. - Can a weak battery cause a P1682 code?
While a weak battery itself typically won’t cause this specific code, it can contribute to voltage inconsistencies that might trigger the code. Always ensure your battery is in good condition. - Is the P1682 code specific to certain car makes?
While P1682 is most commonly associated with General Motors vehicles, similar codes can appear in other makes. Always check your specific vehicle’s documentation for accurate information. - How long does it take to fix a P1682 code?
Repair time can vary widely depending on the cause. Simple fixes like replacing a fuse might take minutes, while more complex issues could require several hours of labor. - Can aftermarket accessories cause a P1682 code?
Improperly installed aftermarket accessories that tap into the ignition system can potentially cause voltage inconsistencies leading to this code. Always ensure add-ons are installed correctly. - Will a P1682 code affect my vehicle’s fuel efficiency?
While the code itself doesn’t directly impact fuel efficiency, the underlying issues causing the code could lead to poor engine performance and decreased fuel economy.
In conclusion, the P1682 code, while specific to the ignition system, can have various causes ranging from simple fuse issues to complex wiring problems or PCM malfunctions. While some aspects of diagnosis and repair can be performed by experienced DIY mechanics, the complexity of modern vehicle electrical systems often necessitates professional intervention. Always prioritize safety and consult with a qualified technician if you’re unsure about any aspect of the repair process. Remember, proper diagnosis is key to effective repair, potentially saving you time and money in the long run.