Powertrain, generic · Hybrid propulsion

P0B04 Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current Low

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

P0B04 indicates that phase V of the auxiliary fluid pump motor carries too little current, usually because the phase is open somewhere between inverter and winding. GM tests it on the Volt (2016) and in the 2018 and 2019 hybrid tables like its U and W siblings: in Run, with normal PWM, more than 50 V on the inverter and a minimum squared current command, the V current is sampled while the rotor sits within 30 degrees of the V axis. Under 1 A for 0.4 s out of 0.6 s (0.08 s windows in 2019) sets a Type A fault. GM bulletin PI1433 for the 2014-15 Spark EV names P0B04 with Service Vehicle Soon and reduced propulsion and points to the pump connector not being latched. P0B01 and P0B07 are phases U and W, P0B05 the high side, P0B03 the general V code.

Likely causes

Pump motor connector not fully seated or latched (Chevrolet Spark EV)
Open circuit in the phase V lead or terminal
Phase V switch in the pump inverter not conducting
Open winding of phase V in the pump motor

Symptoms

  • Service Vehicle Soon light and MIL
  • Reduced propulsion power or limited vehicle speed

Repair estimate

DifficultyHardWorkshop job
Parts and labour€80–2,500
Time1–6 h

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

Parts involved

aux trans pump motor phase vaux trans pump control modulewiring harness

Related codes

P0B01P0B03P0B05P0B07P0C20P0C27

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov.