vinkodex.
Fault code

P1256 fault code.

This code comes up with one known fault.

Manufacturer specific code

Code type

Engine and drivetrain

System

VAG: coolant temperature signal is faulty

VAG code, internal number 17664. The engine control unit found the signal of the coolant temperature sensor (G62) faulty. A false cold signal makes the mixture richer and raises fuel consumption.

The code tells you what the control unit measured, not which part has failed. The same code has several possible causes.

This is a manufacturer specific code. Its meaning differs by brand, so there is no answer to it without knowing the model.

Which known faults it comes up with

Coolant temperature sensor (G62) failure

comfort

The G62 sensor tells the engine control unit how hot the coolant is. If it is faulty, the control unit thinks a warm engine is cold, and runs it rich: hard warm or cold starting, a rough idle, markedly increased fuel consumption, and a dash temperature gauge that jumps around or never reaches its usual reading. The part is cheap and can be replaced in half an hour: the trouble is that many people do not recognise it and replace an injector or a lambda sensor instead. If the fault persists, the rich mixture can destroy the catalytic converter too.

What to check

  • Warm it up and watch the dash temperature gauge: the needle should sit steadily at the middle reading, not jump around
  • Watch a cold start, then a warm start after twenty minutes standing
  • With a code reader look for the 17664 / P1256 code in the engine control unit
2 more steps in the write-up

Information, not an expert opinion

We write the descriptions, and we put the source next to them. A person reviews them before they go out. They are still information, not a technical expert opinion.

  • A fault on the list does not mean the car you are looking at has it.
  • A fault missing from the list does not mean the model is fault-free. Write-ups are made model by model. Not all of them are done.
  • You decide whether to buy. This is no substitute for an inspection. That needs a workshop and a history check.
Details in the terms