P0622 Alternator field control circuit fault: the engine computer sees a bad signal on the wire that tells the alternator how hard to charge

Generator field F control circuit malfunction / alternator field control circuit

P0622 in short

P0622 means the engine computer found a fault in the circuit that controls the alternator's field. The charging system may then stop charging. Chafed wiring, a loose engine ground or a failed alternator are the usual suspects. Get it checked soon, because the battery can run flat and the engine can stall.

The engine computer tells the alternator how much to charge by sending a control signal on a dedicated wire. P0622 is the code for a fault in that field control circuit, and the generic title list from Delaware's inspection program calls it a generator field control circuit malfunction.

If the signal is missing or wrong, charging can be reduced or stop. The car then runs on the battery, which is why owners describe the battery light, dimming lights, electrical items dropping out and, in some cases, the engine shutting off while driving.

The wiring is a documented problem on some vehicles. GM's bulletin PIT5503 names a generator harness rubbing on the A/C line on 2011-2014 trucks, and a 2003 PT Cruiser owner reports the alternator wires shorting against a bolt. A failed alternator or engine computer is possible but should come after the wiring and grounds are checked.

Most likely causes

  1. Chafed or shorted generator wiring, or a corroded connector

    Supported by vehicle data
    Why it ranks here
    GM's PIT5503 names wiring that rubs against the A/C line and shorts on 2011-2014 Silverado and Sierra trucks, and a PT Cruiser owner reports the same kind of short. The reference page also lists damaged or corroded wiring first.
    What would change this
    Rises if the harness shows rub marks or melted insulation, or the code returns after the connector is wiggled. Falls if the wiring and connectors test good.

  2. Loose main engine ground cable (some GM models)

    Supported by vehicle data
    Why it ranks here
    GM's PIC6212 tells technicians to check the main engine ground cable under the starter on a 2016 Cruze that stalled or showed a charging message with P0622. It is specific to that model.
    What would change this
    Rises on a Cruze if the ground cable is loose. Falls if the cable is tight and clean.

  3. Failed alternator

    Common general cause
    Why it ranks here
    The reference page suspects the alternator when the circuits test good. It does not always fix it: a Journey owner replaced the alternator and the problem returned until other parts were dealt with.
    What would change this
    Rises if wiring and grounds test good and charging output is wrong. Falls if the code returns after a new alternator.

  4. Engine computer or its software

    Possible — needs testing
    Why it ranks here
    The reference page calls a defective engine computer relatively common for this code, and a 2005 GM summary links P0622 to a computer calibration. This is a last step after the wiring and alternator.
    What would change this
    Rises if the code returns after the wiring, grounds and alternator are cleared. 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 freeze-frame data, and note the battery voltage with the engine off and then running.

    Low riskTool: OBD-II scan tool, multimeter

    • IfVoltage stays near battery level (about 12 V) with the engine running, or the charge light is on

      It meansThe system is not charging. Look at the wiring and grounds next.

      Go to step 2

    • IfVoltage is normal (about 13.5-14.5 V) and the code is stored but not current

      It meansThe fault may be intermittent. Check wiring for movement-related faults.

      Go to step 2

  2. With the engine off, look at the alternator wiring and connector for rub marks, melted insulation and corrosion, and check the main engine ground cable is tight.

    Use cautionTool: flashlight, basic hand tools

    Warning:Keep hands, clothing and tools away from the belt and fan, and do not let a tool bridge the battery positive terminal and metal. Let the engine cool first.

  3. Ask a dealer whether your VIN has a bulletin or software update covering P0622 and a charging message.

    Low risk

  4. Have a shop test the control wire between alternator and computer for continuity and signal, and test charging output.

    Best left to a shopTool: multimeter, scope, vehicle wiring diagram

    Warning:The charging circuits carry battery current and can arc if shorted. Do not disconnect the battery with the engine running, and probe only with the correct backprobes.

Symptoms

  • Battery or charging warning light, or a Service Charging System message
  • Battery runs down or the car will not crank after sitting
  • Lights dim and radio, wipers or gauges act oddly while driving Gets more serious: stop and have it checked.
  • Engine loses power or shuts off while driving Gets more serious: stop and have it checked.

How to fix

  1. With the engine off and cool, check that the battery terminals and the main engine ground cable are clean and tight.

  2. Look over the alternator wiring for rub marks or burnt connectors and ask a shop to look if you find any.

Parts and cost context

  • Engine control module (ECM / PCM):Treat the engine computer as a last step after wiring, grounds and the alternator are cleared. 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

  • 2016 · Cruze

    Supported by vehicle data

    GM PIC6212 covers a 2016 Cruze that stalled or showed a charging message with P0622 and points to the main engine ground cable under the starter. The bulletin is from the NHTSA cache and its current status is not verified.

  • 2011–2013 · Silverado 1500

    Supported by vehicle data

    GM PIT5503 names the generator harness rubbing the A/C line on 2011-2013 Silverado trucks. Unverified bulletin.

  • PIC6212Status unverified

    Stall while driving or charging message with P0622: engine ground cable

    2016cruze · NHTSA 10083075

    Tells the technician to check the main engine ground cable under the starter for looseness on a Cruze that stalled or shows a charging message with P0622.

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

  • PIT5503 (chevrolet)Status unverified

    Service Charging System message with P0621/P0622: generator harness

    2011–2013silverado-1500, silverado-2500-hd, silverado-3500-hd · NHTSA 10113959

    Generator harness can rub on the A/C compressor line and short; inspect, repair and add conduit.

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

GMC

  • 2011–2014 · Sierra 2500 HD

    Supported by vehicle data

    Same GM PIT5503 harness issue on the 2011-2014 Sierra 2500. Unverified bulletin.

  • PIT5503 (gmc)Status unverified

    Service Charging System message with P0621/P0622: generator harness

    2011–2014sierra-2500-hd · NHTSA 10113959

    Generator harness can rub on the A/C compressor line and short; inspect, repair and add conduit.

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

Ford

  • 2004 · F-150

    Supported by vehicle data

    Two Ford summaries link the charge warning light to P0622 on the 2004 F-150 but do not state a repair.

  • 17262Status unverified

    Charging system warning indicator on, possible P0622

    2004f-150 · NHTSA 10004915

    Names the charge warning light and P0622 on the 2004 F-150. The NHTSA summary does not say what the repair is.

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

Chrysler

  • 2003 · PT Cruiser

    Supported by vehicle data

    A 2003 PT Cruiser owner reports P0622 after a charging failure and a shop finding the alternator-to-computer wires shorted by a bolt near the frame. Owner report only.

Dodge

  • 2009–2012 · Journey

    Supported by vehicle data

    Journey owners report P0622 with a battery light and stalling. One replaced the alternator and still lost power until the battery was also replaced.

No curated relationships for P0622 yet.

All Charging and starting codes

P0622 questions

Is it safe to drive with P0622?

Not for long. If the charge light is on, the battery is supplying the car and can run flat. Drive only as far as needed to get it checked and stop if lights dim or power drops.

Does P0622 always mean a bad alternator?

No. Wiring and ground faults are documented on some models, and one owner's alternator replacement did not clear the problem. Check the wiring first.

Sources and review

  1. NHTSA complaint ODI 10564717 — NHTSA (consumer complaint database, local flat-file cache)
  2. NHTSA complaint ODI 11114445 — NHTSA (consumer complaint database, local flat-file cache)
  3. GM PIC6212: stalled while driving, battery light or Service Charging System message, P0622 (2016 Cruze) — General Motors (via NHTSA manufacturer communications flat file)
  4. P0622 trouble code page — TroubleCodes.net
  5. GM PIT5503: Service Charging System message or SES lamp with P0621 and/or P0622 (2011-2014 Silverado, Sierra) — General Motors (via NHTSA manufacturer communications flat file)
  6. On-Board Diagnostic Trouble Codes (generic code title list) — Delaware Division of Motor Vehicles ,
  7. NHTSA complaint ODI 10778397 — NHTSA (consumer complaint database, local flat-file cache)
  8. Ford 17262: charging system warning indicator on with possible P0622 (2004 F-150) — Ford (via NHTSA manufacturer communications flat file)
Last reviewed
Written by
Saurabh K.
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