P2D26

Code

Generic P — Powertrain

Coolant Pump E Control Circuit Performance/Stuck Off

Brand: Generic

Type: P — Powertrain

Views: UK: 28 EN: 31 RU: 22

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Page language: EN

Causes

Open, short or high-resistance in pump power or ground circuit
Corroded, loose or damaged connector at pump
Blown fuse or faulty pump relay
Failed electric coolant pump motor (seized or burned windings)
PCM / control module driver fault or software/calibration issue
Intermittent wiring break due to chafing, heat or vibration

Symptoms

Malfunction Indicator Lamp (MIL) / Check Engine light ON
Reduced or no coolant circulation from pump E when commanded
Higher than expected engine coolant temperature or localized hot spots
Heater performance degraded if circuit affects heater loop
Possible engine derate / limp mode on systems that rely on coolant control
Audible silence from pump when it should run (no whir or vibration)

What to check

Read freeze frame and readiness data; confirm P2D26 is current and note conditions
Using a scan tool, attempt to command Coolant Pump E ON and observe status
Visually inspect pump connector and wiring for corrosion, damage, or disconnection
Check related fuses and relays for continuity and correct operation
Backprobe pump connector while commanding pump: check supply voltage and ground
Measure pump motor resistance (connector disconnected) and compare to specification

Signal parameters

Expected supply voltage at pump when commanded ON: ~10–14.5 V (vehicle battery range)
Expected control signal (if PWM controlled): 0–100% duty cycle depending on command
Typical PWM frequency range (varies by vehicle): ~20–200 Hz (manufacturer-specific)
Typical pump motor resistance (motor only): roughly 0.2–5 ohms (varies by pump design)
Typical running current: ~2–15 A depending on pump size; locked-rotor current will be higher
When stuck off: commanded ON in scanner but measured voltage/current are near 0 V / 0 A

Diagnostic algorithm

Retrieve and record freeze frame, related codes, and PCM data. Verify conditions when the code set.
With a scan tool, command Coolant Pump E ON while observing PCM command and pump feedback/status. Note whether PCM reports pump ON and whether pump responds.
Visually inspect the pump connector, pins and wiring harness for corrosion, bent pins, melted insulation or loose terminals. Repair or clean as necessary.
Check fuses and relays for the pump circuit; replace if faulty. Verify relay control and coil continuity.
Backprobe the pump power and ground pins while commanding the pump ON: confirm battery voltage at power pin and a good ground. If voltage is present but pump does not run, proceed to motor tests.
With connector disconnected, measure pump motor winding resistance. Compare to factory spec. A very high/OL or short to ground indicates a bad motor.
If resistance looks reasonable, bench-test the pump with a fused 12 V supply (observe polarity and safety): the pump should run and draw a steady current. Measure running current; excessive current indicates mechanical binding or electrical fault.
If pump runs on bench test, perform continuity and resistance checks from PCM connector to pump connector to locate high resistance/open in wiring. Repair any harness damage and verify grounds.
If wiring and pump are good but pump still does not operate under command, suspect PCM output driver failure or software issue. Check for technical service bulletins and perform PCM tests per manufacturer procedure; consider module reflash or replacement only after wiring/pump confirmed good.
After repairs, clear codes, retest by commanding pump and perform a road/operational test under the conditions where the code originally set. Confirm no recurrence.

Likely causes

Blown fuse or faulty relay for the pump circuit
Open or corroded connector at the pump
Failed pump motor (no rotation / excessive current draw)
PCM output driver fault (if wiring and pump test good)
Intermittent wiring fault where harness flexing changes continuity

Fault status

⚠️ Status

PCM commanded Coolant Pump E ON but pump did not operate or circuit performance was outside expected parameters (low/no current or voltage drop detected).

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours

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