B1349
Heated Backlite Relay Short To Battery
Body Chassis/Safety Heated Rear Window 🟢 Low — Fix at next service
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What This Actually Means
In plain language — no jargon

The heated rear window relay is stuck in the 'on' position, constantly sending full battery voltage to the heating element instead of cycling properly. Think of it like a light switch that's jammed in the pressed position—it stays on even when you try to turn it off.

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Symptoms You May Notice
3 known symptoms for this code
Heated rear window stays on continuously or won't turn off
Rear window defroster inoperative or unresponsive to controls
Battery drains quickly due to constant relay activation
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Embedded Systems Insight
What the ECU/ECM is actually computing

The ECU monitors the relay control circuit voltage and current draw. It expects the relay to cycle on and off under normal operation, with periodic duty-cycle pulses. When the relay shorts directly to battery voltage, the ECU detects an abnormally high voltage on the relay control line (12V continuous instead of pulsed) and excessive current draw.

Voltage & Parameter Thresholds

Parameter Normal Range Fault Condition
Relay Control Voltage 0–5V pulsed or variable Constant 12V or near-battery voltage
Current Draw 0.5–2A cycling >3A continuous
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Diagnostic & DIY Fix Guide
Check these in order — from cheapest to most complex
1
Heated backlite relay
Locate the relay in the fuse/relay box (usually under dashboard or engine bay), note its position, remove it, and install a new relay of the same part number.
2
Wiring harness to relay
Inspect the relay socket and wiring for melted insulation, corrosion, or moisture; reseat the relay or replace damaged wire segments.
3
Fuse for heated backlite circuit
Check and replace the corresponding fuse if blown; if it blows again after relay replacement, suspect ongoing short in wiring.