P0E1A

Code

Generic P — Powertrain

Hybrid/EV Battery Pack Coolant Pump B Control Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 27 EN: 37 RU: 22

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Page language: EN

Causes

Open or damaged wiring in pump B control circuit
Corroded/loose connector at pump or controller
Failed coolant pump motor (electrical failure or mechanical seizure)
Blown fuse or faulty relay supplying pump circuit
High resistance/poor ground in pump circuit
Faulty vehicle control module (ECU/BCM) driver or software fault

Symptoms

Battery pack coolant pump B not running when commanded
Hybrid/EV warning light or battery/thermal warning message
Battery temperature rising or thermal derate of propulsion system
Reduced vehicle performance or limited charge/discharge capability
No audible pump noise from pump B or abnormal pump noise
Possible HVAC/cabin temperature effect if shared coolant circuit

What to check

Retrieve and record freeze-frame data and stored DTCs with a scan tool
Visual inspection of pump B, wiring harness, connectors and mounting for damage or contamination
Check fuses and relays related to battery coolant pumps
Using a scan tool monitor command/feedback for pump B (on/off command and status)
Back-probe connector at pump while commanding ON to verify presence of control voltage and ground
Measure continuity and resistance of control and ground wires from pump to control module

Signal parameters

Control command: typically a switched battery/auxiliary voltage or PWM control (0 V when off, near vehicle battery/aux bus when commanded on). Exact voltage varies by design — consult service manual.
Expected supply voltage at pump when commanded ON: approximately vehicle 12–14 V (or specified auxiliary voltage); may be higher on some systems — refer to OEM spec.
Motor resistance: typically low (indicative of a low-impedance motor); open/infinite resistance indicates open circuit. Exact ohms vary by pump design.
Current draw when running: measurable steady current. A stuck/musical motor may draw excessive current; an open circuit draws no current. Exact amperage varies by pump design.
PWM frequency (if used): commonly in the hundreds to low thousands of Hz; verify with OEM information.

Diagnostic algorithm

Safety first — follow manufacturer high-voltage isolation/safety procedures before accessing HV components. Depressurize coolant system and allow to cool if needed.
Connect a scan tool, read codes and freeze frame data. Note any related codes (other cooling pumps, fuses, communication errors).
Perform a visual inspection of pump B, harness, and connectors. Repair any obvious damage or corrosion.
Verify fuses and relays for the pump circuit; replace if blown or intermittent.
Using a scan tool, command pump B ON while observing live data. Listen/observe for pump operation.
Back-probe pump connector while commanded ON: measure control voltage and ground presence. If no voltage at connector but module is commanding, suspect wiring/connector fault between module and pump.
If voltage present at connector but pump does not run, isolate and apply direct auxiliary power (per safety procedures) to pump to confirm pump motor condition. If pump runs on direct power, suspect control/ground or PWM driver issue.
If pump does not run on direct power, measure motor winding resistance; infinite/open indicates internal motor fault — replace pump.
Check continuity and resistance of wires between pump connector and control module; repair any opens or high resistance. Wiggle test harness while monitoring voltage to find intermittent faults.
If wiring and pump test good but no proper control, inspect/replace module driver or perform module reflash per OEM procedures.
After repairs, clear codes, perform forced pump operation cycles via scan tool and verify proper operation and that code does not return during road/test conditions.