Powertrain, generic (extended)

P2B58 Engine Coolant Flow Control Valve Motor Current High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modeNo

P2B58 reports that the electric motor driving the engine coolant flow control valve draws too much current. GM documents the check for its 3.0-litre inline-six Duramax diesel: in the 2025 table 25OBDG04B the driver stage flags a current above 5.5 A, and 80 failures in 100 samples taken every 12.5 ms set a Type B fault, so the MIL follows on the second trip. Enabling needs more than 11 V on the powertrain relay and an engine that is not cranking. A seized rotary valve, debris in the housing or a motor with shorted windings are typical reasons. GM bulletin 21-NA-149 lists P2B58 for LM2 trucks with a chafed engine harness. Heating and warm-up may suffer while the valve is stuck.

Likely causes

Rotary valve stiff or seized from deposits or debris in the housing
Valve motor with shorted turns
Chafed engine harness on GM LM2 (bulletin 21-NA-149)

Symptoms

  • MIL on after the second drive with the fault
  • Slow warm-up or weak cabin heat
  • Fans may run more often as a precaution

Repair estimate

DifficultyHardWorkshop job
Parts and labour€100–1,800
Time1–10 h

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

Parts involved

engine coolant flow control valvewiring harnessecm

Related codes

P2B59P2B5AP2B5BP2B60

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