ECM/PCM Power Input Signal Range/Performance

Possible causes

• CommonWeak or failing battery
• CommonCorroded earth strap or module earth point
• CommonCorroded or loose battery terminals
• CommonCharging system fault - a failing alternator or regulator
• PossibleBlown fuse or failing relay in the module supply
• PossibleDamaged supply wiring

What you might notice

• Erratic running or stalling
• Limp mode
• Several unrelated warning lights
• Slow cranking
• Module resetting while driving
• Check engine light on

What to check, in order

1. Check battery voltage, the terminals and the earth straps first. An unstable supply produces faults across unrelated systems, and chasing those individually wastes a great deal of time.
2. Measure battery voltage with the engine off and again running, and compare both against specification.
3. Perform a voltage drop test on the module's supply and earth. High resistance in a corroded connection produces exactly this with nothing looking wrong.
4. Check the charging system output under load - lights and heated screen on.
5. Do not order a control module on the strength of a power supply code. The module is reporting a problem, not necessarily having one.