P1682 Engine computer’s two ignition voltage feeds disagree (GM)

Ignition 1 switch circuit 2 (GM)

P1682 in short

On Chevrolet, GMC, Buick, Cadillac and Saab, P1682 means the engine computer saw its two ignition voltage feeds disagree. A failing ignition relay, a corroded or loose fuse-block terminal, or a battery drain are typical causes. Have it checked soon; it can cause no-starts, reduced power or stalling.

GM engine computers receive ignition voltage on two circuits supplied through different relays and compare them. If the two differ by more than about 3 volts while the powertrain relay is on, the computer stores P1682. GM classes it as a Type A code.

Because it is about ignition power reaching the computer, the symptoms are electrical: delayed or extended cranking, intermittent crank or no start (especially in the cold), reduced engine power, or a stall. GM has linked it to the engine controls ignition relay on 2014 trucks and the Impala, to the relay or underhood fuse block terminals on 2019–2020 heavy-duty trucks and SUVs, and to arcing or corrosion at the underhood fuse block on the Traverse, Acadia and Enclave.

Battery drains can set it too. On some 2016–2019 Silverado and Sierra trucks, water in the headlamp connections kept modules awake and flattened the battery, and GM lists P1682 with battery draw and no start on 2007–2013 Traverse, Acadia, Enclave and Outlook.

Pick your make

P1682 is a manufacturer-specific code: its meaning depends on who built the car.

Other makes: meaning not verified. Check with a scan tool that reads manufacturer definitions.

Most likely causes

  1. Failing engine controls ignition relay

    Supported by vehicle data
    Why it ranks here
    GM bulletins for 2014 Silverado and Sierra 1500, the 2014–2015 Impala and 2019–2020 heavy-duty trucks and SUVs point at the ignition relay, and GM service information replaces the relay when the circuits test good.
    What would change this
    Rises with intermittent crank or no-start and good circuit tests. Falls if a circuit or terminal fault is found.
    How to test the engine controls ignition relay

  2. Arcing, corroded or loose terminal at the underhood fuse block

    Supported by vehicle data
    Why it ranks here
    GM PIT5643 and bulletin 19NA276 cover the Traverse, Acadia and Enclave, where arcing or corrosion at a fuse block connector can cause reduced power or a stall with P1682 and P0689. PIP5729 names fuse block terminals on 2019–2020 trucks.
    What would change this
    Rises if the fuse block connector shows heat marks or corrosion. Falls if terminals are clean and tight.
    How to test the underhood fuse block (engine compartment fuse box)

  3. Battery drain or low battery (headlamp water intrusion, modules staying awake)

    Supported by vehicle data
    Why it ranks here
    GM bulletins list P1682 with battery draw and no start on 2007–2013 crossovers and with water in headlamp connections draining the battery on 2016–2019 Silverado and Sierra 1500.
    What would change this
    Rises if the battery keeps going flat overnight or there is water in a headlamp. Falls if a parasitic draw test is normal.

  4. Open or short in the ignition feed or relay control circuit

    Common general cause
    Why it ranks here
    GM service information tests the relay terminals, the ignition voltage feedback circuit and the relay control circuit for opens and shorts as part of P1682 diagnosis.
    What would change this
    Rises if a circuit test finds an open, short or high resistance. Falls if all circuits test good.

What to test first

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

  1. Test the battery and charging system and look for signs of a battery drain, such as a battery that goes flat overnight.

    Low riskTool: battery tester or multimeter

  2. Ask a GM dealer whether your VIN has a bulletin for P1682. GM has issued them for the Traverse, Acadia, Enclave, Silverado, Sierra, Impala, Cruze and Verano.

    Low risk

  3. Have a shop test the ignition relay terminals, the ignition voltage feedback circuit and the relay control circuit, as GM service information describes.

    Best left to a shopTool: digital multimeter, wiring diagram

    Warning:This involves back-probing fuse block and engine computer circuits. Leave it to a shop.

Symptoms

  • Delayed or extended cranking before the engine starts
  • Intermittent crank or no start, especially in cold weather
  • Battery that goes flat overnight
  • Reduced engine power message
  • Engine stalls while driving Gets more serious: stop and have it checked.

How to fix

  1. Have the battery and charging system tested.

  2. Ask a GM dealer whether your VIN has a bulletin for P1682 before replacing the engine computer or sensors.

Parts and cost context

  • Engine controls ignition relay:GM replaces the engine controls ignition relay when circuit tests pass. Labour varies; get a quote.
  • Underhood fuse block (engine compartment fuse box):On the Traverse, Acadia and Enclave GM’s bulletins repair arcing or corrosion at the fuse block connector; ask whether the terminal can be repaired. Labour varies; get a quote.

Labor varies by vehicle and shop; get a quote before you approve a repair.

Compare used part prices on PartPriceGuide

On your vehicle

Chevrolet

  • 2013–2017 · Traverse

    Supported by vehicle data

    GM bulletins 19NA276 and PIT5643 link P1682 (often with P0689) to arcing or corrosion at the underhood fuse block, with reduced power or a stall. Whether the bulletin is still current is not verified.

  • 2009–2013 · Traverse

    Supported by vehicle data

    On earlier models GM lists P1682 with battery draw and no start. Whether the bulletin is still current is not verified.

  • 2014–2015 · Impala

    Supported by vehicle data

    GM PIC5971A points to the KR75 engine controls ignition relay for intermittent crank or no start with P1682. Whether the bulletin is still current is not verified.

  • 19NA276Status unverified

    Reduced engine power and/or stall with P1682 and/or P0689

    2013–2017traverse · issued · NHTSA 10170495

    Repair information for reduced power or stall with P1682 and/or P0689. Also covers Buick Enclave and GMC Acadia.

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

  • PIT5643Status unverified

    P0689 and/or P1682: arcing or corrosion at the fuse block

    2013–2014enclave · issued · NHTSA 10151875

    Check for arcing or corrosion on terminal 51 of the X3 connector at the underhood fuse block. Also covers Acadia and Traverse.

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

  • PIT4649BStatus unverified

    SES MIL with P1682, battery draw and/or no start

    2007–2013acadia · issued · NHTSA 10245303

    Also covers Enclave, Outlook and Traverse.

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

  • PIP5729Status unverified

    SES lamp with P1682 (Ignition 1 Switch Circuit 2)

    2019–2020silverado-2500, tahoe, suburban · issued · NHTSA 10176315

    May be caused by a faulty ignition relay or underhood fuse block terminal; P0101 may also be stored. Also covers Sierra, Yukon and Escalade.

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

  • PIC5971AStatus unverified

    Intermittent crank/no start with P1682

    2014–2015impala · issued · NHTSA 10059179

    Possible cause the KR75 engine controls ignition relay.

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

  • PI1422Status unverified

    Intermittent crank/no start in cold climates, P1682

    2011–2015cruze · issued · NHTSA 10113563

    Also covers Buick Verano.

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

  • PIT5546EStatus unverified

    Water in headlamp connections: dead battery, no crank, P1682

    2016–2019silverado-1500 · issued · NHTSA 10160689

    A short from water in the headlamp keeps modules awake and drains the battery. Also covers Sierra 1500.

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

GMC

  • 2007–2017 · Acadia

    Supported by vehicle data

    Same bulletins as the Traverse: battery draw on earlier models, fuse block arcing or corrosion on 2013–2017. Whether the bulletin is still current is not verified.

  • 19NA276Status unverified

    Reduced engine power and/or stall with P1682 and/or P0689

    2013–2017traverse · issued · NHTSA 10170495

    Repair information for reduced power or stall with P1682 and/or P0689. Also covers Buick Enclave and GMC Acadia.

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

  • PIT5643Status unverified

    P0689 and/or P1682: arcing or corrosion at the fuse block

    2013–2014enclave · issued · NHTSA 10151875

    Check for arcing or corrosion on terminal 51 of the X3 connector at the underhood fuse block. Also covers Acadia and Traverse.

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

  • PIT4649BStatus unverified

    SES MIL with P1682, battery draw and/or no start

    2007–2013acadia · issued · NHTSA 10245303

    Also covers Enclave, Outlook and Traverse.

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

  • PIT5253AStatus unverified

    Intermittent crank/no start with P1682

    2014sierra-1500 · issued · NHTSA 10111867

    Follow service information; replace the engine controls ignition relay if diagnostics lead there. Also covers Silverado 1500.

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

Buick

  • 2008–2017 · Enclave

    Supported by vehicle data

    Same bulletins as the Traverse and Acadia. Whether the bulletin is still current is not verified.

  • 19NA276Status unverified

    Reduced engine power and/or stall with P1682 and/or P0689

    2013–2017traverse · issued · NHTSA 10170495

    Repair information for reduced power or stall with P1682 and/or P0689. Also covers Buick Enclave and GMC Acadia.

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

  • PIT5643Status unverified

    P0689 and/or P1682: arcing or corrosion at the fuse block

    2013–2014enclave · issued · NHTSA 10151875

    Check for arcing or corrosion on terminal 51 of the X3 connector at the underhood fuse block. Also covers Acadia and Traverse.

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

  • PIT4649BStatus unverified

    SES MIL with P1682, battery draw and/or no start

    2007–2013acadia · issued · NHTSA 10245303

    Also covers Enclave, Outlook and Traverse.

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

  • P0101Airflow sensor reading doesn't match what the engine computer expects for the throttle opening

    Shares causes Supported by vehicle data

    GM PIP5729 notes that 2019–2020 heavy-duty trucks and SUVs with P1682 may also store P0101, and some had a MAF sensor replaced when the ignition relay or fuse block terminal was the real fault.

  • P0562System voltage low

    Shares causes Possible — needs testing

    Both can come from a weak or drained battery. GM links P1682 to battery drains, and a failing battery is a top cause of P0562.

All Charging and starting codes

P1682 questions

Can P1682 cause my car not to start?

Yes. GM bulletins describe intermittent crank or no start with P1682, often traced to the ignition relay, a fuse block terminal or a drained battery.

Is P1682 the same on every make?

No. This page covers the GM meaning (Chevrolet, GMC, Buick, Cadillac and Saab). Other makers may use P1682 for something else.

Sources and review

  1. GM bulletin 19NA276: reduced engine power and/or stall with P1682 and/or P0689 (2013–2017 Enclave, Traverse, Acadia) — General Motors / NHTSA ,
  2. GM PI1422: intermittent crank/no start in cold climate, P1682 (2011–2015 Cruze, Verano) — General Motors / NHTSA ,
  3. GM PIT5253A: intermittent crank/no start with P1682, engine controls ignition relay (2014 Silverado 1500, Sierra 1500) — General Motors / NHTSA ,
  4. GM PIC5971A: intermittent crank/no start with P1682, engine controls ignition relay (2014 Impala) — General Motors / NHTSA ,
  5. GM PIP5729: SES lamp with P1682 (Ignition 1 Switch Circuit 2) (2019–2020 HD trucks, Tahoe, Suburban, Yukon, Escalade) — General Motors / NHTSA ,
  6. DTC P0685, P0689, P0690 or P1682 (LFW), 2011 Saab 9-4X service information — Saab Automobile / General Motors (Saab WIS online archive)
  7. GM PIT5643: P0689 and/or P1682, arcing or corrosion at X3 terminal 51 of the underhood fuse block (2013–2014 Enclave, Acadia, Traverse) — General Motors / NHTSA ,
  8. GM PIT4649B: SES MIL with P1682, battery draw and/or no start (2007–2013 Acadia, Enclave, Outlook, Traverse) — General Motors / NHTSA ,
  9. GM PIT5546E: water in headlamp connections, dead battery, no crank, P1682 (2016–2019 Silverado 1500, Sierra 1500) — General Motors / NHTSA ,
  10. How To Test an Alternator — AA1Car.com (Larry Carley)
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Written by
Saurabh K.
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