Code
P102B
DACIA
P — Powertrain
Starter signal - circuit malfunction
AI status
Completed
Completed
100%
Causes
- Blown fuse for starter/ignition circuit
- Faulty starter relay or relay socket
- Open, shorted or corroded wiring/connectors between ignition switch, PCM (ECU) and starter/relay
- Faulty starter solenoid or starter motor
- Weak or discharged battery or poor battery terminals/ground
- Faulty ignition switch or start/stop button circuitry
Symptoms
- No crank (key turned but starter does not engage)
- Intermittent cranking or crank only after jiggling key/wiring
- Starter spins but engine does not turn over, or starter fails to disengage
- Dash lights dim when attempting to start
- Start only when bypassing relay or jumping starter control
- Possible related warning lights or immobiliser indicator
What to check
- Check battery voltage at rest and during cranking; ensure battery >= 12.4 V at rest
- Inspect starter fuse(s) and in-line fusible links for continuity
- Verify starter relay operation (listen for click; swap with known good relay if available)
- Visually inspect wiring and connectors at starter, relay, fusebox and PCM for corrosion, damage or loose pins
- Check engine/chassis grounds and battery terminal connections for tightness and corrosion
- Scan for additional DTCs and immobiliser status; check for stored starter/ignition-related faults
Signal parameters
- Control line idle: no active start signal (approx 0 V to open/high impedance depending on design)
- Control line active: switches to battery voltage (~11–14 V) OR provides ground path depending on vehicle switching design; should be stable while cranking
- Starter solenoid coil resistance: typically low (roughly 0.5–3 ohms) — varies by design; very high or open indicates coil fault
- Starter cranking current: high transient current (tens to hundreds of amps); low terminal voltage under load indicates battery/connection problem
- Control pulse duration: present while key is held to START position or until engine fires (no rapid pulsing expected)
Diagnostic algorithm
- Verify battery health and terminals. Recharge or replace battery if voltage or CCA insufficient.
- Use a scan tool to confirm P102B and check for related DTCs (immobiliser or starter/relay codes). Note freeze frame if available.
- Inspect fuses, fusible links and starter relay. Replace faulty items and re-check code.
- With ignition OFF, visually inspect and wiggle wiring/connectors from battery, starter, relay, and PCM for damage or corrosion. Repair as needed.
- Backprobe the starter control terminal at the starter/relay. Have an assistant turn key to START and observe voltage: confirm expected switching (battery voltage or ground).
- If no proper control signal, trace continuity from starter control terminal back to relay/ignition switch/PCM. Repair open/shorted wiring or replace connectors.
- If control signal from PCM/ignition switch is present but starter does not operate, bench-test starter and solenoid or measure solenoid coil resistance and inrush current; replace starter if faulty.
- If PCM is expected to provide the control and no output is present after wiring checks, confirm immobiliser is not inhibiting start; verify PCM grounds and supply voltages.
- Repair identified faults, clear codes, and perform repeat start tests and a road test to confirm the issue is resolved.
Likely causes
- Open or short in starter control wire between PCM/ignition switch and starter/relay
- Defective starter relay or relay contacts
- Poor battery/ground connection causing low control voltage
- Faulty starter solenoid not responding to control signal
- Immobiliser preventing starter signal
Fault status
Status
Starter control circuit malfunction detected (P102B). Starter may not engage; inspect starter circuit, relay, fuses, battery and immobiliser.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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Code
P102B
RENAULT
P — Powertrain
- Starter signal - circuit malfunction
AI status
Completed
Completed
100%
Causes
- Blown fuse for starter/ignition circuit
- Faulty starter relay or relay socket
- Open, shorted or corroded wiring/connectors between ignition switch, PCM (ECU) and starter/relay
- Faulty starter solenoid or starter motor
- Weak or discharged battery or poor battery terminals/ground
- Faulty ignition switch or start/stop button circuitry
Symptoms
- No crank (key turned but starter does not engage)
- Intermittent cranking or crank only after jiggling key/wiring
- Starter spins but engine does not turn over, or starter fails to disengage
- Dash lights dim when attempting to start
- Start only when bypassing relay or jumping starter control
- Possible related warning lights or immobiliser indicator
What to check
- Check battery voltage at rest and during cranking; ensure battery >= 12.4 V at rest
- Inspect starter fuse(s) and in-line fusible links for continuity
- Verify starter relay operation (listen for click; swap with known good relay if available)
- Visually inspect wiring and connectors at starter, relay, fusebox and PCM for corrosion, damage or loose pins
- Check engine/chassis grounds and battery terminal connections for tightness and corrosion
- Scan for additional DTCs and immobiliser status; check for stored starter/ignition-related faults
Signal parameters
- Control line idle: no active start signal (approx 0 V to open/high impedance depending on design)
- Control line active: switches to battery voltage (~11–14 V) OR provides ground path depending on vehicle switching design; should be stable while cranking
- Starter solenoid coil resistance: typically low (roughly 0.5–3 ohms) — varies by design; very high or open indicates coil fault
- Starter cranking current: high transient current (tens to hundreds of amps); low terminal voltage under load indicates battery/connection problem
- Control pulse duration: present while key is held to START position or until engine fires (no rapid pulsing expected)
Diagnostic algorithm
- Verify battery health and terminals. Recharge or replace battery if voltage or CCA insufficient.
- Use a scan tool to confirm P102B and check for related DTCs (immobiliser or starter/relay codes). Note freeze frame if available.
- Inspect fuses, fusible links and starter relay. Replace faulty items and re-check code.
- With ignition OFF, visually inspect and wiggle wiring/connectors from battery, starter, relay, and PCM for damage or corrosion. Repair as needed.
- Backprobe the starter control terminal at the starter/relay. Have an assistant turn key to START and observe voltage: confirm expected switching (battery voltage or ground).
- If no proper control signal, trace continuity from starter control terminal back to relay/ignition switch/PCM. Repair open/shorted wiring or replace connectors.
- If control signal from PCM/ignition switch is present but starter does not operate, bench-test starter and solenoid or measure solenoid coil resistance and inrush current; replace starter if faulty.
- If PCM is expected to provide the control and no output is present after wiring checks, confirm immobiliser is not inhibiting start; verify PCM grounds and supply voltages.
- Repair identified faults, clear codes, and perform repeat start tests and a road test to confirm the issue is resolved.
Likely causes
- Open or short in starter control wire between PCM/ignition switch and starter/relay
- Defective starter relay or relay contacts
- Poor battery/ground connection causing low control voltage
- Faulty starter solenoid not responding to control signal
- Immobiliser preventing starter signal
Fault status
Status
Starter control circuit malfunction detected (P102B). Starter may not engage; inspect starter circuit, relay, fuses, battery and immobiliser.
Repair difficulty: Medium
Diagnostic time: 1.0-2.5 hours
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