B2468

Code

Other B — Body

Aux Heater Coolant Pump Circuit Short to Ground

Brand: Other

Type: B — Body

Views: UK: 23 EN: 36 RU: 26

AI status

Completed

ready

Completed 100%

Page language: EN

Causes

Damaged or chafed wiring harness contacting chassis ground
Corroded or loose connector terminals
Failed aux coolant pump motor with internal short
Failed pump control module or driver transistor shorted to ground
Blown fuse or shorted relay causing abnormal circuit behavior
Improper previous repair or aftermarket component causing pin damage

Symptoms

Malfunction Indicator Lamp (MIL) or service message illuminated
Aux heater coolant pump does not run or runs continuously
Reduced cabin heating efficiency or longer warm-up time
Coolant temperature control anomalies (overheating or failure to warm)
Possible parasitic battery drain

What to check

Scan for stored and pending codes, record freeze-frame data and freeze conditions
Visually inspect pump, wiring harness routing, and connectors for damage or corrosion
Check related fuses and relays for continuity and proper operation
Backprobe pump control connector and measure voltage with key ON and during commanded operation
Disconnect pump connector; check resistance from control circuit to chassis ground for short
Substitute known-good pump or connector if available to isolate component vs wiring

Signal parameters

Key ON, pump not commanded: control circuit voltage generally at battery voltage (~11–14 V) for high-side control or near 0 V for low-side (ground) switching designs — refer to vehicle-specific wiring
Pump commanded ON: control line should switch (either pull to ground or apply battery voltage) and current draw typically in the low amp range (commonly 1–8 A depending on pump); sudden 0 V or near 0 Ω to ground indicates short
Open circuit: infinite resistance or very high resistance between pump circuit and control module
Short to ground: low resistance (

Diagnostic algorithm

Read and record all related DTCs and freeze-frame data. Attempt an active command of the aux pump with a scan tool and note response.
Visually inspect pump, connector, and harness along full routing from pump to control module for abrasion, heat damage, or corrosion. Repair visible damage.
With ignition OFF, disconnect pump connector. Using an ohmmeter, measure resistance between the control pin and chassis ground. A very low resistance indicates a short to ground in wiring or module.
With ignition ON (engine off), backprobe the control connector at the pump and measure voltage. If control is expected high and reads ~0 V, suspect short to ground or failed driver.
Disconnect the control module/ECU connector (if accessible) and check if the short is in harness or module: measure resistance from harness control wire to ground with the module disconnected. If short clears, suspect module; if still shorted, continue wiring repair.
If harness removed from suspicion, bench-test or substitute a known-good pump to confirm pump internal condition. Measure pump current draw when commanded; excessive current suggests motor fault.
Repair or replace damaged wiring, connectors, pump, or control module as identified. Protect and secure harness away from chafing points and apply dielectric grease to connectors if appropriate.
Clear DTCs and perform functional test under the same conditions that set the code to confirm repair. Re-scan for codes after a road or thermal cycle as required.

Likely causes

Wire insulation abrasion where harness contacts body or engine
Water intrusion/corrosion at pump connector causing low resistance to ground
Pump motor windings internally shorted
Control module output stage shorted (low-side driver)
Connector pushed out of housing or bent terminal shorting to ground

Fault status

⚠️ Status

Auxiliary heater coolant pump control circuit fault — short to ground detected on pump control circuit. Pump may not operate correctly; wiring or control module may be damaged.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours