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P0655 – Engine Hot Lamp Output Control Circuit Malfunction (OBD2)

P0655 means "Engine Hot Lamp Output Control Circuit Malfunction". The control unit has detected a fault in the electrical circuit of the warning lamp and output circuit: the signal or control current is missing or outside the expected window. The code does not say whether the value is too high or too low, so the wiring and the component itself both have to be checked.

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P0655 quick summary

Fault codeP0655
MeaningEngine Hot Lamp Output Control Circuit Malfunction
SystemPowertrain (Engine & Transmission)
VehiclesGeneric OBD2
SeverityLow
Can I drive?Yes. The engine is not affected, but a non-working warning lamp means you may miss other faults – have it repaired before the inspection.
Repair cost€0 – €300

What warning lamp and output circuit codes mean

These codes mean the control unit has detected a fault in a circuit it uses to switch a warning lamp or send a signal to another module – for example the Check Engine lamp, generator lamp or fuel cap lamp.

The engine control unit drives several indicator lamps and output signals directly or via the instrument cluster: the malfunction indicator lamp (MIL, P0650), generator lamp (P0621, P0623), fuel cap lamp (P0624), engine hot lamp (P0655) and the serial communication to the driver display (P0644).

On modern cars most lamps are controlled over the CAN bus, so these codes are more common on older vehicles or specific makes. The fault usually lies in the wiring, a connector or the instrument cluster, not in the engine.

Although these faults do not affect how the engine runs, a Check Engine lamp that does not work is a safety and inspection issue: you would not be warned about other faults.

On VAG vehicles (VW, Audi, Škoda, Seat, Cupra), VCDS and older VAG testers can show this code as the five-digit VAG code 17039 (P0655). Both numbers mean the same fault.

Symptoms of P0655

  • Warning lamp does not light up during the bulb check
  • Warning lamp stays on permanently
  • Display shows wrong or no information
  • Code stored without other symptoms
  • Failed inspection (MIL not working)

Most common causes of P0655 (most likely first)

Mechanic's Pro Tip

A Check Engine lamp that never lights up during the bulb check is a red flag when buying a used car – it may have been disabled to hide faults.

  1. 1.Damaged wire or loose, corroded connector at the warning lamp and output circuit

    Most likely

    Green or white corrosion, pushed-back pins and chafed insulation near hot or moving parts are the most common findings.

  2. 2.Faulty warning lamp and output circuit

    An internal break or short in the component itself.

  3. 3.Blown fuse or missing supply voltage

    If several codes appeared at the same time, check the shared fuse, relay or ground point first.

  4. 4.Wiring fault in the lamp or output circuit

  5. 5.Instrument cluster fault

  6. 6.Burnt-out bulb (older vehicles)

  7. 7.Control unit output driver fault

Step-by-step diagnostic guide

  1. 1

    Do a bulb check

    Switch on the ignition and see whether all warning lamps light up briefly.

  2. 2

    Check the circuit with a multimeter

    With the ignition off, unplug the warning lamp and output circuit and the control unit connector (or back-probe), then check each wire between them for continuity and for shorts to ground and to battery voltage. Compare the component's resistance or supply voltage with the value in the repair manual.

    Multimeter: Wire continuity: below about 1 Ω. Wire to ground with both connectors unplugged: no continuity. Supply/reference with ignition on: usually 5 V for sensors, battery voltage for actuators.

  3. 3

    Read codes in all modules

    Read engine and instrument cluster codes.

  4. 4

    Command the lamp

    Use the scan tool output test to switch the lamp on and off.

  5. 5

    Check wiring

    Check the wiring between the control unit and the cluster for opens and shorts.

  6. 6

    Repair and verify

    Repair the wiring, bulb or cluster and repeat the bulb check.

Frequently asked questions

Can I keep driving with P0655?

Yes. The engine is not affected, but a non-working warning lamp means you may miss other faults – have it repaired before the inspection.

How much does it cost to fix P0655?

Typical repair costs are 0 € – 300 €, depending on the cause and the vehicle. The most common fixes are: damaged wire or loose, corroded connector at the warning lamp and output circuit; faulty warning lamp and output circuit; blown fuse or missing supply voltage. Always confirm the cause with the tests above before buying parts.

Is a Check Engine lamp circuit code serious?

Not for the engine, but you would not be warned about other faults and the car can fail inspection.

Why does the code mention the generator lamp?

On some vehicles the engine control unit drives the battery/charging warning lamp. A fault in that circuit sets P0621 or P0623.

What is the difference between P0655 and similar codes?

P0655 belongs to a group of codes for the same component that differ in the type or location of the fault: P0621 – Generator Lamp L Control Circuit Malfunction; P0623 – Generator Lamp Control Circuit; P0624 – Fuel Cap Lamp Control Circuit; P0644 – Driver Display Serial Communication Circuit; P0650 – Malfunction Indicator Lamp (MIL) Control Circuit Malfunction. The tests on this page apply to the whole group; the type of fault tells you where to start.

Related fault codes

This guide is for information only. Working on vehicles can be dangerous — if you are unsure, have the car checked by a qualified mechanic. Values can differ between model years; always check the manufacturer's repair information.