P0650 Check engine light circuit fault: the engine computer sees a problem in the circuit that switches the malfunction indicator lamp

Malfunction indicator lamp (MIL) control circuit malfunction

Severity not verified — if the car runs badly, have it inspected

Neither source rates how serious P0650 is. The fault is in the lamp circuit, so the check engine light itself may not warn you of other problems until it is fixed.

Source: how we rate severity

P0650 in short

P0650 means the engine computer found a fault in the circuit that controls the check engine light. The light may flash, stay on or not come on at all. Loose grounds and damaged or corroded wiring are the usual causes. A fault inside the computer is rare.

Delaware's inspection program lists P0650 as a malfunction indicator lamp control circuit malfunction. TroubleCodes.net describes it as the computer detecting a problem in the lamp's control circuit or the lamp itself.

The lamp may flash, stay lit or fail to light. A light that does not work can hide other faults, so the circuit is worth fixing.

TroubleCodes.net lists damaged, corroded or disconnected wiring in the CAN bus, ground straps left loose after maintenance, and, rarely, a fault in the control module's lamp circuit. It advises owners to check system voltage, visible wiring and grounds, and to avoid randomly unplugging connectors.

Most likely causes

These are general causes for this code across vehicles. None is specific to one make or model.

  1. Loose ground straps or damaged, corroded or disconnected wiring

    Common general cause
    Why it ranks here
    The reference page puts wiring and ground faults first, including grounds left loose after recent maintenance.
    What would change this
    Rises if the code appeared after recent work under the hood or a ground strap is loose or corroded. Falls if grounds and wiring test good.

  2. MIL circuit fault inside the engine computer or another control module

    Possible — needs testing
    Why it ranks here
    TroubleCodes.net calls this rare and says it needs professional equipment to isolate, so it comes after the wiring checks.
    What would change this
    Rises if wiring, grounds and voltage all test good. Falls if any earlier check finds a fault.
    How to test the engine control module (ecm / pcm)

What to test first

Start at step 1. Each result tells you what it means and where to go next.

  1. Read all codes and check system voltage, the ground straps and any visible wiring, especially if the code appeared after recent maintenance.

    Low riskTool: OBD-II scan tool, multimeter

  2. Have a shop trace the MIL circuit and check the control modules and the CAN bus.

    Best left to a shopTool: scan tool, wiring diagram

    Warning:Unplugging connectors at random can damage control modules and set new codes; follow the maker's procedure and disconnect the battery as it directs.

Symptoms

  • Check engine light flashes, stays on, or does not come on at startup
  • Stored or pending P0650

How to fix

  1. With the engine off, check that battery cables and ground straps are tight and clean, especially after recent maintenance.

On your vehicle

Buick

  • 2001–2002 · Century

    Supported by vehicle data

    GM bulletin 01584 covers P0650 set after powertrain control module replacement. Whether it is still current is not verified.

  • 2001–2002 · Regal

    Supported by vehicle data

    GM bulletin 01584 covers P0650 set after powertrain control module replacement. Whether it is still current is not verified.

  • 01584-buickStatus unverified

    P0650 set after PCM replacement

    2001–2002century, regal · issued · NHTSA 10005424

    Buick listing of a GM bulletin about P0650 set after powertrain control module replacement. Only the NHTSA summary was read; it gives no repair.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

Chevrolet

  • 2001–2002 · Impala

    Supported by vehicle data

    GM bulletin 01584 covers P0650 set after powertrain control module replacement. Whether it is still current is not verified.

  • 2001–2002 · Monte Carlo

    Supported by vehicle data

    GM bulletin 01584 covers P0650 set after powertrain control module replacement. Whether it is still current is not verified.

  • 01584-chevroletStatus unverified

    P0650 set after PCM replacement

    2001–2002impala, monte-carlo · issued · NHTSA 10005424

    Chevrolet listing of a GM bulletin about P0650 set after powertrain control module replacement. Only the NHTSA summary was read; it gives no repair.

    We couldn't confirm whether this bulletin is still current, so it doesn't count as confirmation.

No curated relationships for P0650 yet.

All Engine computer (ECM/PCM) codes

P0650 questions

Can a loose ground strap set P0650?

TroubleCodes.net lists ground straps left improperly tightened after maintenance as a possible cause.

Sources and review

  1. On-Board Diagnostic Trouble Codes (generic code title list) — Delaware Division of Motor Vehicles
  2. P0650 trouble code page — TroubleCodes.net
  3. 01584: P0650 set after PCM replacement — Buick
  4. 01584: P0650 set after PCM replacement — Chevrolet
Last reviewed
Written by
Saurabh K.
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This page explains what a code usually means; it is not a substitute for a professional inspection. How we source and review · Report an error

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