B2449

Code

Other B — Body

Aux Heater Glow Plug Circuit Short to Ground

Brand: Other

Type: B — Body

Views: UK: 25 EN: 47 RU: 30

AI status

Completed

ready

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Page language: EN

Causes

Damaged or chafed heater harness contacting chassis ground
Corroded or water-intruded connector at the glow plug or heater module
Failed auxiliary glow plug with internal short
Shorted control/ground wire due to pinched routing or improper repairs
Faulty heater control module or output transistor shorted to ground
Aftermarket heater or improper installation causing wiring faults

Symptoms

Auxiliary heater inoperative or disabled
Heater warning or auxiliary-heater fault indicator set on dash
Difficulty pre-heating or reduced cabin/engine warm-up in cold conditions
Battery drain or blown fuse when heater is commanded
DTC stored and possibly other related heater codes present

What to check

Read DTCs and freeze-frame data from all control modules; note history and status
Perform a visual inspection of auxiliary heater wiring, connectors and mounting for damage, corrosion, or signs of heat
Check relevant fuses and relays for open or evidence of overheating
With ignition off, disconnect the auxiliary heater/plug connector and inspect pins for corrosion and shorts
Measure resistance between the heater supply pin and chassis ground with connector disconnected
Backprobe the heater control connector and measure voltage at the supply and control pins while commanding the heater on (use caution)

Signal parameters

Normal supply voltage when heater commanded: battery voltage (~11–14 V) at the heater supply pin (may be switched or fused)
Control output: either steady battery voltage or a PWM signal from heater control module when active (verify with oscilloscope/voltmeter)
Good glow-plug/heater element resistance: typically low but finite (varies by design); a short to ground will show near 0 Ω between supply feed and chassis ground
Open/disabled circuit when not commanded: control output should be near 0 V or module-specific idle state (consult manufacturer spec)

Diagnostic algorithm

Safety first: park vehicle, set parking brake, allow components to cool and disconnect battery if required by manufacturer procedures
Read and record all stored and pending codes from modules; clear codes and attempt to re-run to confirm repeatability
Visually inspect entire auxiliary-heater wiring harness, connectors, grommets and mounting for abrasion, pinching, corrosion, melted insulation or fluid ingress
Check fuses/relays in heater supply circuit for continuity and signs of overheating; replace as necessary
With ignition off, disconnect the auxiliary-heater connector. Measure resistance between the heater supply pin and chassis ground. A near-zero reading indicates a short to ground in the harness or heater
Measure individual glow-plug/heater element resistance (if accessible) to look for internal shorted element; compare to service specs or other known-good unit
Reconnect and backprobe the heater supply and control pins. Command the heater on (via scan tool) and measure voltage/current. If the control output is low or source is pulled to ground only when commanded, suspect a short in the harness/heater or a module output fault
Isolate the fault: disconnect harness at intermediate connectors to localize the short between connector locations; if disconnecting the heater eliminates the short, the heater or its connector is suspect
If harness and heater check good, test or substitute the heater control module (or its output transistor) per manufacturer procedures
After repair, clear codes, re-test heater operation through several on/off cycles and road conditions, and verify no recurrence
Note: follow manufacturer-specific procedures and voltage/current limits; avoid applying direct battery power to unknown connectors.

Likely causes

Wiring insulation abrasion where harness rubs a metal edge
Corroded connector pins at the glow plug or auxiliary heater unit
One or more glow plug elements failed and are shorted internally
Shorted output transistor inside the heater control module (module failure)
Water ingress causing conductive path to chassis ground

Fault status

⚠️ Status

Control module detected a short-to-ground condition in the auxiliary heater/glow-plug circuit. The module may disable the heater output and store a fault to prevent damage. Repair should locate and eliminate the low-resistance path to chassis ground before clearing the code.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-2.0 hours