P0B04Electric/Auxiliary Transmission Fluid Pump Motor Phase V Current Low
- Generic OBD-II code · Powertrain
- Turns on the check-engine light
- Matters for the ITP
- Can trigger limp mode
- How the car detects it
- 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.
- What you may notice
- Service Vehicle Soon light and MIL
- Reduced propulsion power or limited vehicle speed
- Likely causes
- LikelyPump motor connector not fully seated or latched (Chevrolet Spark EV)
- PossibleOpen circuit in the phase V lead or terminal
- PossiblePhase V switch in the pump inverter not conducting
- RareOpen winding of phase V in the pump motor
- Inspection (ITP)
- Matters for the ITP. While the check-engine light is on, the car fails the emissions check.
- Repair
- Hard · Usually a job for a workshop.Typical cost: €80 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.