Code
P1629
DAEWOO
P — Powertrain
Glow lamp fault
AI status
Completed
Completed
100%
Causes
- Burnt-out or blown indicator bulb/LED
- Blown fuse for glow lamp or glow system
- Faulty glow lamp relay or control module
- Open, shorted or corroded wiring/connectors between lamp, relay and ECU
- Faulty glow plugs or heater element causing abnormal current draw
- Poor ground connection at lamp, relay or ECU
Symptoms
- Glow plug indicator (pre-heat lamp) does not illuminate with ignition ON
- Glow lamp stays on continuously or flashes abnormally
- Hard starting or extended cranking in cold conditions
- Possible MIL illumination depending on ECU behavior
- Intermittent glow lamp operation
What to check
- Scan tool: read freeze frame and confirmed DTCs; check live data for glow lamp status
- Visual inspection of indicator lamp, instrument cluster, fuse box and wiring for damage or corrosion
- Check fuses related to glow/ignition circuits
- Inspect and test glow lamp bulb/LED and socket for continuity
- Verify relay operation (swap with known good relay if available)
- Measure voltage at lamp socket and relay control with key ON/engine cranking
Signal parameters
- Indicator lamp supply voltage with ignition ON (approx. battery voltage expected)
- Voltage on relay control coil when glow is requested (key ON/start sequence)
- Ground integrity at lamp and relay (- near 0Ω expected)
- Relay contact voltage to lamp when energized (should be near battery voltage)
- Glow plug/heater circuit current draw (spec depends on vehicle, typically several amps per plug)
- Resistance of each glow plug (compare to manufacturer specification)
Diagnostic algorithm
- Confirm the P1629 code and note any other related codes (glow plug or heater circuit codes).
- Perform a visual inspection of the dash indicator lamp, instrument cluster connector, associated fuses and relays for obvious damage or corrosion.
- With ignition ON, check for battery voltage at the indicator lamp socket. If no voltage, check upstream fuse and wiring to the fuse/relay.
- Test the indicator lamp (bulb or LED) by bench testing or swapping cluster/indicator with known good, or measure continuity through the lamp.
- Check glow lamp relay operation: energize relay and verify switching voltage to the lamp circuit; substitute known-good relay if available.
- Inspect and test wiring continuity between the relay, indicator lamp and ECU; check for shorts to battery or ground and for high-resistance connections.
- With engine off, measure resistance of each glow plug and compare to spec; check total current draw of the glow heater circuit during a cold start request.
- If wiring, relay and lamp are good but abnormal current or open/short in heater circuit is found, diagnose and repair glow plugs/heater elements and associated harness.
- If all external components test good and wiring is intact, consider ECU/PCM output failure—perform manufacturer-recommended ECU tests before replacement.
- After repairs, clear codes, perform several key-on/start cycles and re-scan to confirm code does not return and lamp behaves correctly.
Likely causes
- Lamp filament or LED failed
- Relay coil or contacts stuck/failed
- Fuse blown in glow lamp circuit
- Damaged connector or pin corrosion at instrument cluster or relay
- High resistance in glow plug circuit triggering lamp fault detection
Fault status
Status
Glow lamp fault detected. The control module has identified an abnormal condition in the glow lamp/indicator circuit or associated wiring/relay/heater components. The indicator may be inoperative, stuck on, or reporting irregular status.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
Similar codes
Repair manuals
Manual library for DAEWOO
75
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