Emissions

P00FF — Control Module Requested MIL Illumination

Severity: medium Drive with care, to a shop

What P00FF means

P00FF relates to a request from a control module, most often the body control module (BCM), to turn on the malfunction indicator lamp (MIL). It does not point to one failed sensor. The code's definition is not clearly standardized and can vary by manufacturer, so it mainly tells you a fault exists somewhere that needs to be tracked down using other codes and scan data.

Symptoms

  • Check engine light (MIL) on
  • Occasional rough idle or reduced performance
  • Possible emissions test failure
  • Other warning lights or communication errors between modules

Possible causes

  1. Another module requested the MIL because of a fault stored under a different code
  2. Damaged wiring or corroded connectors in a related circuit
  3. BCM or engine control module software glitch
  4. Faulty auxiliary fuel or air system component (pump, valve, sensor)
  5. Low supply voltage or a poor ground at a module

How to diagnose

  1. Scan all modules for codes, not just the engine computer, and save freeze-frame data
  2. Address any other stored codes first, since P00FF is likely secondary
  3. Test battery voltage, terminals and engine and body grounds
  4. Inspect BCM and ECM harnesses and connectors for corrosion, moisture and chafing
  5. Look up the code's definition in the manufacturer's service information
  6. Check for software updates and technical service bulletins
  7. Clear the code and see whether it returns

Common fixes

  • Repair the root cause of the code that triggered the MIL request
  • Repair wiring and clean or replace faulty connectors
  • Reflash or update BCM or ECM software at a dealer or qualified shop
  • Replace a failed auxiliary system component once testing confirms it

Questions and answers

What does P00FF mean?

It means another control module, such as the BCM, asked for the check engine light to be turned on. The exact meaning varies by manufacturer, so look at any accompanying codes.

Can I drive with P00FF?

Briefly, yes, if the car drives normally. Find the cause soon to avoid damage or emissions problems.

Will the code go away on its own?

The light may go out after several good drive cycles, but if the fault remains the code will return. Clearing it alone does not fix the problem.

This is general information about the code. The meaning can differ between makes and models: a scan tool and the repair manual for your car will show the exact cause.