Code
P261A
Generic
P — Powertrain
Coolant Pump B Control Circuit/Open
Views:
UK: 31
EN: 115
RU: 45
AI status
Completed
Completed
100%
Causes
- Blown fuse or open relay for coolant pump circuit
- Open, shorted, corroded, or damaged wiring/connectors between ECM and pump
- Failed coolant pump (stator/brushes/motor) or internal connector failure
- Faulty ECM/PCM driver or internal relay/transistor failure
- Connector contamination, poor ground, or water intrusion
- Intermittent connection due to broken terminal or bent pin
Symptoms
- Malfunction Indicator Lamp (MIL) illuminated
- Auxiliary coolant pump (B) not running or intermittent operation
- Reduced secondary coolant circulation, reduced heater or A/C performance
- Possible engine overheating under certain conditions
- Stored fault P261A in ECM freeze frame / freeze data
What to check
- Retrieve all stored and pending DTCs and freeze frame data; note operating conditions
- Visually inspect pump, wiring harness, connectors and grounds for damage or corrosion
- Check related fuse(s) and relay(s) for the coolant pump circuit
- Measure connector voltage at pump with ignition ON and during commanded ON
- Measure pump motor resistance and current draw while supplying known good power (fused jumper)
- Perform continuity and resistance checks from ECM driver pin to pump connector
Signal parameters
- Key ON, engine OFF: supply voltage at pump power terminal ≈ battery voltage (11–14 V) when fuse/relay closed
- Commanded ON: pump motor current typically in the 1–10 A range (varies by model); expect measurable current flow
- Pump motor DC resistance typically low (approx. 0.5–10 Ω depending on pump design) — refer to vehicle spec
- ECM control signal may be switched to ground or a PWM output; PWM frequency often 50–500 Hz (manufacturer-specific)
- Open-circuit symptom: no voltage or no current at pump when command is active
Diagnostic algorithm
- Confirm code: Clear codes and attempt to reproduce fault; record freeze frame and freeze data.
- Visual inspection: Inspect pump, mounting, connector for corrosion, water ingress, bent pins, and secure grounds.
- Check fuses/relays: Verify fuse continuity and proper relay operation for coolant pump circuit; replace if faulty.
- Backprobe pump connector: With key ON and with ECU commanding pump ON (active test or during normal conditions), measure supply voltage and ground. If no power, check upstream fuse/relay.
- Verify pump operation: Apply fused 12 V directly to pump ground/power to confirm motor runs and measure current draw. If pump does not run, replace pump.
- Continuity to ECM: With power removed, check continuity between pump control pin and ECM control pin and measure resistance to ground; repair any open or high-resistance wiring.
- Check ECM output: Use an oscilloscope or multimeter to verify ECM control signal (steady ground, switched +12 V or PWM). If ECM does not output when commanded but wiring is good, consider ECM driver fault.
- Inspect for intermittent faults: Wiggle test harness and connectors while monitoring circuit for intermittent opens.
- Repair and retest: Repair wiring/connectors or replace pump/relay/ECM as indicated. Clear codes and perform road/functional test to confirm repair.
- If ECM replacement is considered, confirm all wiring, grounds and loads are correct to avoid damaging new module.
Likely causes
- Corroded or disconnected pump connector at pump
- Open circuit in harness (broken wire) between pump and ECM
- Failed pump motor drawing no current
- Blown fuse or stuck open relay in pump power feed
- ECM output driver failed (less common)
Fault status
Status
Coolant Pump B Control Circuit/Open — ECM detected open or no-drive on coolant pump B control circuit. MIL on; pump may not operate when commanded.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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