Code
P1616
DAEWOO
P — Powertrain
Main relay mal
Views:
UK: 2
EN: 2
RU: 3
AI status
Completed
Completed
100%
Causes
- Faulty main (engine) relay (contacts stuck open/closed or coil failure)
- Blown fuse or fusible link in the ECU power feed
- Poor battery voltage or weak battery
- Corroded/loose relay socket or connector pins
- Damaged wiring or open/short to relay control or power circuits
- Faulty ground connection for ECM or relay coil
Symptoms
- MIL/Check Engine Lamp illuminated
- Engine cranks but will not start or intermittent no-start
- Complete loss of engine power or stalling
- No fuel pump or injector pulse when key is ON/CRANK
- Intermittent ECU power or resetting while driving
- Accessory or electrical anomalies tied to ECU feed
What to check
- Read and record freeze frame / stored codes; clear and retest
- Visual inspection of main relay, fuse box, relays and wiring for corrosion, overheating or damage
- Check battery voltage (should be ~12.4–12.8 V at rest; >11 V while cranking)
- Verify main relay presence and correct seating in socket; inspect pins
- Check ECU power and ground pins for battery voltage and good ground with key ON
- Swap main relay with a known-good relay of same type (if available) and retest
Signal parameters
- Relay coil control voltage: should be ~12 V when relay is commanded ON (key ON/START or ECU command)
- Relay output (supply) voltage: battery voltage (~12 V) present at relay output when energized
- Coil resistance: typical small-relay coil tens to a few hundred ohms (verify with service data)
- No-voltage condition: if relay not energized, relay output should be near 0 V relative to battery ground
- Continuity: low resistance between battery positive and ECM supply pin when relay closed
Diagnostic algorithm
- Connect scan tool, read freeze frame and pending codes. Note when and under what conditions code set.
- Visually inspect main relay, relay socket and harness for corrosion, melting, or water ingress. Check related fuses and fusible links.
- Verify battery voltage. Recharge or replace weak battery before continuing.
- With ignition ON (engine OFF), measure voltage at the relay coil control terminal and at the relay supply terminal. Compare to battery voltage.
- Crank engine while monitoring relay coil/control voltage to confirm proper activation under cranking.
- If relay is not being commanded but should be, trace control circuit back to immobilizer and ECM outputs; check for anti-theft inhibiting signal.
- Manually energize the relay (or apply 12 V to relay coil) with proper precautions: verify relay output feeds ECU and that engine attempts to start. If engine starts with relay manually energized, suspect control circuit or relay driver.
- Swap the main relay with a known-good identical relay (if available) and retest to confirm relay vs. wiring/ECM fault.
- Check continuity and resistance of power feed from battery + to relay output and from relay output to ECM supply pin; check grounds for low resistance to chassis negative.
- If wiring and relay test good but problem persists, check ECM power input circuitry and immobilizer interface or consult manufacturer service data. Replace faulty components per service procedure.
- After repair, clear codes and perform a driving/starting cycle to verify the issue does not return.
Likely causes
- Worn or failed main relay
- Loose/corroded connector at relay or ECM
- Blown ECU power fuse
- Open/short in battery feed or relay control wire
- Bad ground at ECU/relay
- Intermittent immobilizer cut-off
Fault status
Status
Main relay malfunction detected — ECU power feed or relay control circuit fault. Inspect main relay, fuses, connectors, wiring and grounds; verify immobilizer/ECM control.
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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