Powertrain, generic · Vehicle speed, idle control and auxiliary inputs

P05C3 Engine Coolant Pressure Sensor Circuit Range/Performance

Check engine lightOn
EmissionsNot relevant
Drive cycleRequired
Limp modeNo

An engine coolant pressure sensor (5 V reference, ratiometric signal) measures pressure in the cooling circuit; in a sealed circuit pressure rises with temperature, so deviations reveal leaks or a loose cap – described in Navistar and GE patents for commercial and rail engines. No manufacturer document available to us uses P05C2–P05C6 for passenger cars; CARB requires input components to be checked for circuit faults, range and plausibility. P05C3 means the signal is valid but implausible – for example not near ambient pressure with a cold, equalised circuit, or not following temperature during warm-up. A real pressure loss from a leak or faulty cap can also land here.

Likely causes

Sensor drifting or stuck (fouled pressure port, scale)
Real pressure fault: leak, faulty radiator or expansion tank cap
Air in the cooling system after filling
Combustion gas in the coolant (head gasket)

Symptoms

  • Check engine light or warning (depending on the maker)
  • Coolant loss or smell with a real leak
  • Possibly rising temperature

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–400
Time0.5–2.5 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

coolant pressure sensorsensor wiringengine control module

Related codes

P05C2P05C4P05C5P0117P2560P0217

References: law.cornell.edu, patents.google.com, patents.google.com.