Powertrain, generic (extended)

P2603 Coolant Pump A Control Circuit High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2603 means the drive line of electric coolant pump A reads high - usually a short to the supply side, or an overcurrent seen by the driver stage. Ford's 2020-2023 gasoline OBD summary assigns pump A to the auxiliary high-temperature loop for cabin heating and sets P2602/P2603 when the smart driver reports a fault within 5 s. For the 3.6 L LLT, GM's 2008 table checks the after-run pump for a circuit fault to voltage (pending code only, no warning light). VW's 2014 books use a current threshold: about 0.60-1.20 A on the Passat and CC, 5.5-10 A on the Touareg. Under CARB, output components need monitoring for circuit faults. P2600 is the open circuit, P2601 performance, P2602 the low-side fault. Heater output or after-run cooling may be lost.

Likely causes

Control wire shorted to battery voltage
Seized or sluggish pump drawing excessive current
Faulty driver stage in the ECM

Symptoms

  • Fault code stored; MIL depends on the maker (GM 2008 LLT table none, GM 2023 ECM table Type B)
  • Weak cabin heating
  • Higher coolant temperature after hot shutdown

Repair estimate

DifficultyMediumDIY possible
Parts and labour€60–500
Time0.5–2.5 h

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

Parts involved

coolant pump aactuator wiringecm

Related codes

P2600P2601P2602

References: law.cornell.edu, gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov.