P0831 OBD-II Trouble Code: Clutch Pedal Switch "A" Circuit Low

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Cost of diagnosing the P0831 code

P0831 is a diagnostic trouble code (DTC) for "Clutch Pedal Switch "A" Circuit Low". This can happen for multiple reasons and a mechanic needs to diagnose the specific cause for this code to be triggered in your situation. Our certified mobile mechanics can come to your home or office to perform the Check Engine Light diagnostic. Once we are able to diagnose the problem, you will be provided with an upfront quote for the recommended fix and receive $20.00 off as a credit towards the repair. All our repairs are backed by our 12-month / 12,000-mile warranty.

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What the P0821 code means

In vehicles with manual transmissions, the clutch position sensor (CPS) is also sometimes called the clutch start switch, clutch safety switch or clutch interlock switch since it needs to be closed before the starter can engage, in order to prevent the vehicle from being started while in gear. `A P0821 code means that the powertrain control module (PCM) has registered a malfunction with the clutch position sensor.

What causes a P0821 code?

Most commonly, a P0821 code is due to a failed or mis-adjusted CPS . Other causes might include problems with wiring or electrical connectors, such as open circuits, shorts or corrosion.

What are the symptoms of a P0821 code?

Symptoms may not present themselves at all, or could include:

  • No-start condition
  • Engine can start without the clutch depressed
  • Stored code
  • Illuminated malfunction indicator lamp (MIL)
  • Inoperative cruise control

How does a mechanic diagnose a P0821 code?

A scan tool/code reader and digital volt/ohmmeter (DVOM) will be needed for diagnosis and repair. The DVOM may be the more useful, as it can show the technician what the clutch pedal switch is actually doing and not just what the PCM registers. A repair manual for the vehicle and factory wiring diagram can help show the exact location of the switch.

  • Check to ensure all connectors are properly seated in place and there is no corrosion, water infiltration or bent/backed out pins. Any of these can increase resistance and prevent the ECM from recognizing a signal. Repair/replace as needed.

  • With the parking brake set, disconnect CPS sensor “B.” Use your DVOM to measure continuity and check the sensor’s response with the clutch pedal depressed or released. Check your repair manual to find out if the CPS should read “open” or “closed” in each position, as this can vary from model to model.

  • If resistance does not change with the pedal released or depressed, it could be a problem with the switch. If the switch is adjustable, you may be able to position it closer to the pedal. If the switch is open or internally shorted, it will need to be replaced.

  • If resistance across the switch in each position is within spec, the problem may be in the circuit. Disconnect the appropriate connector at the PCM and reconnect the CPS sensor. Repeat the resistance check at the PCM connector.

  • If resistance does not change with the clutch depressed or released, the problem is likely in the wiring harness. Disconnect the CPS and recheck. A short circuit or any kind of resistance may interfere with the CPS.

  • If resistance changes as it should, the PCM may be reporting a false circuit problem. See remarks.

Common mistakes while diagnosing P0821 code

Often, a no-start condition with the P0821 code is misdiagnosed as a problem with the starter.

How serious is a P0821 code?

A P0821 code can result in:

What repairs can fix a P0821 code?

Replacement or adjustment of CPS, or replacement/repair of corroded or damaged wiring to CPS.

Additional comments for consideration for P0821 code

Some drivers have the bad habit of “riding the clutch,” with one foot on the clutch even when it’s fully released. A foot that is only slightly on the clutch pedal can be enough to prevent the CPS from sensing that the clutch is released, resulting in a P0821 code. It has also been reported that in some General Motors models, the PCM may not recognize CPS switches in rapid succession. In other words, by pressing and releasing the clutch a few times, the PCM may fail to recognize further switches from the CPS, resulting a P0822 code.

Need help with a P0821 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6220.

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