Code
P1210
SCION
P — Powertrain
Injector control circuit malfunction
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UK: 1
EN: 5
RU: 4
AI status
Completed
Completed
100%
Causes
- Blown fuse or faulty power/ignition relay supplying injector circuits
- Damaged injector wiring harness (chafing, corrosion, broken wires)
- Poor or corroded connector pins at injector or ECM
- Failed fuel injector (shorted or open coil)
- Faulty ECM/injector driver transistor
- Low battery/poor ground connection or high resistance ground
Symptoms
- Check Engine Light (MIL) on
- Rough idle or misfire under load or at idle
- Reduced engine power, hesitation, or stalling
- Fuel smell if injector stuck open (rare)
- Poor fuel economy
What to check
- Read and record freeze frame and all stored codes with scan tool
- Verify battery voltage (while cranking and idling) and confirm good grounds
- Inspect related fuses and relays for continuity and proper operation
- Visually inspect injector connectors and wiring for damage, corrosion, pin push-out or burnt insulation
- Measure injector coil resistance and compare to vehicle spec
- Backprobe injector connector with scan tool commanded test or use oscilloscope to view injector waveform
Signal parameters
- Injector supply voltage: ~battery voltage (~12 V) at injector power feed (verify with spec)
- Injector driver output: pulsed ground or high-side drive controlled by ECM; pulses with PW (pulse width) from ~1–10 ms depending on load
- Typical injector coil resistance: check service spec (commonly low-impedance ~2–5 Ω or high-impedance ~12–16 Ω) — always use manufacturer spec
- Idle pulse frequency: synchronized with engine speed; duty/pulse width varies with load
- Expected waveform: clean rectangular pulses with steady battery feed; no sustained short to ground or open circuit signature
Diagnostic algorithm
- Retrieve codes and freeze-frame data. Clear codes and attempt to re-run to confirm repeatability.
- Verify battery voltage ≥ 12.4 V with engine off and ≥ 13.5 V with engine running. Poor voltage can affect diagnostics.
- Inspect fuses/relays for injector power and replace if blown.
- Visually inspect injector wiring and connectors for damage, corrosion, or pin issues. Repair as needed.
- With ignition OFF, measure each injector coil resistance and compare to spec. Replace any injector out of spec.
- With key ON (engine off) verify battery feed present at injector power pins. If power missing, trace back to fuse/relay/wiring.
- Backprobe injector control pin while cranking/running or use a noid light to confirm injector driver pulsing. If no pulse, check ECM driver output and wiring continuity to ECM.
- Use an oscilloscope to inspect injector waveforms for abnormal current draw (short/poor driver) or irregular pulses. Swap injectors between cylinders to see if code follows injector or stays with circuit.
- Check continuity and resistance between injector connector and ECM pin, and check for short to ground or to battery.
- If wiring and injectors test good and waveform/pulsing absent or abnormal from ECM, consider ECM/driver replacement or professional bench testing/repair.
- After repair, clear codes and perform a drive cycle to verify fault does not return.
Likely causes
- Connector corrosion at injector or short to ground in harness
- Open or shorted injector coil (internal short or open winding)
- Faulty injector driver inside the ECM
- Blown fuse or poor power/ground to multiple injectors
Fault status
Status
Injector control circuit malfunction — ECM detected abnormal injector driver/wiring behavior. Check injector(s), wiring, power/ground, fuses/relays, and ECM driver.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
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