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P1682 Code: Meaning, Causes, Symptoms, and Fixes

  • Cars Explained
  • Silas Smith
  • 5 minutes

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So your car is showing the diagnostic trouble code P1682, not starting, and you do not know what to do. DTCs or engine trouble codes are how the car tells you something is wrong with it. These five-digit codes are either general or manufacture dependent, and knowing about them can save the car from further damage and help you save money on repairs.


The trouble code P1682 is one such problem that shows up in most car models. But this is a manufacture-dependent issue that has different meanings in different vehicles. We will be looking at the P1682 code in GM vehicles, including GMC, Oldsmobile, Buick, Chevrolet, Cadillac, Hummer, Saturn, Pontiac, and Isuzu models. Read ahead to learn about the meaning, causes, symptoms, and possible fixes of trouble code P1682.

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What does code P1682 mean?

The OBD II code P1682 is defined as “Driver 5 Line 2” in General Motors vehicles. This code is set when the Engine Control Module(ECM) finds a voltage difference that is higher than the maximum allowed threshold between two circuits- Circuit 1 and Circuit 2 (In GM terminology).

In non-GM vehicles, the P1682 trouble code is defined as ‘Ignition 1 Switch Circuit 2,’ which has a similar meaning to the former definition. So the steps for diagnosis can also be similar.

In GM vehicles, these are the two circuits responsible for providing the ECM with battery power. One of these circuits passes through the ignition switch and relay to ECM to provide power to the Throttle Actuator Control(TAC) system. The other circuit runs through the crank relay and fuse to supply power to all remaining circuits of the ECM.

In short, this error code shows up when something is wrong with the ignition switch. Before going into the P1682 code fix, you need to know some common symptoms that can help you identify the problem easily.

What are the symptoms of this code?


  • Stalling engine: The engine cranks, but the car is in a no-start condition. In some cases, there will be no crank and no start.
  • Weak or dead battery.
  • Noises from the hood: Due to wear and tear, the moving parts or bearings of the circuitry might be making a grinding noise.
  • Headlights are dimming: You may also notice the warning lights dim. Occasionally, the lights burn brighter when you are slowing down and dimmer as you accelerate.
  • Illuminated warning light(Engine Light ON) and the stored trouble code.
  • Loose Fuse or Blown fuse box.

In some cases, there may be other codes present. Some other damage or error might have occurred due to the main issue in such cases.

What causes code P1682?

On most GM models, the causes of code P1682 will be similar. You can see a few of these causes below.

  • Defective ignition switch: This is the most common cause of the code. Repairing or replacing the ignition switch will prompt the code to go away.
  • Ignition switch harness: The code will show up if the harness is either open or shorted.
  • Ignition switch circuit: The electrical connections in the circuit may either be damaged or disconnected. Damaged insulations and bare wires can also be the issue here.
  • Faulty fuses or fuse boxes: Some fuse boxes are known to deform when parked under the sun for a long time. This can result in the wiring inside the fuse box either loosening or breaking.
  • Fuel pumps: Defective or malfunctioning fuel pumps can also trigger the P1682 code.
  • Defective ECM: In some cases, the ECM may be faulty. In that case, you may have to look at a replacement to clear the code.

How to fix the P1682 code?

Once a proper diagnosis is carried out, you can try one of the following steps as a fix.

  • Replace the ignition switch: This will most likely solve the issue, and the code will vanish. It is advised to replace a damaged switch to prevent getting stranded in the middle of a journey.
  • Replace the fuses or fuse box: If the first step does not work, it is time for further inspections. The first place to look is the fuse box for loose connections in the wiring and connectors.
  • Change the relays: If the relays are in poor physical condition, replace them to check whether the code is still there or not. If not, move on to see the fuel pump’s health.
  • Replacing the ECM: The entire ECM might be faulty in some cases. It will be the fix that can cost you a lot but replacing the entire control module is the only solution in this scenario.


If you cannot figure out the problem or are unsure about the code and symptoms, it would be better to consult with a technician. Since the reduced power can cause the car to go into a no-start state, it is better to get help as soon as possible.

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