Code
P0201
HUMMER
P — Powertrain
Injector 1 Control Circuit
Views:
UK: 7
EN: 33
RU: 49
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring to injector #1
- Poor or corroded connector or pin at injector or ECU
- Faulty fuel injector (coil open/short)
- Faulty PCM/ECM injector driver
- Blown fuse or poor power/ground to injector rail
- Water intrusion or physical damage to harness
Symptoms
- Check Engine Light (MIL) illuminated
- Rough idle or vibration from cylinder #1
- Cylinder #1 misfire (possible stored P0301)
- Reduced engine power or hesitation
- Poor fuel economy and increased emissions
- No-start or hard-start conditions (in some cases)
What to check
- Read freeze frame and scan data; note misfire counts and operating conditions
- Perform visual inspection of injector #1 connector, wiring and ECM connector
- Check for related codes (e.g., P0200, P0202–P0208, P0301)
- Verify power and ground at injector connector with key ON
- Measure injector coil resistance with a multimeter
- Backprobe injector signal while cranking or idling to confirm pulse
Signal parameters
- Injector supply voltage: approximately battery voltage (typically ~11–14 V with key ON and engine running)
- Injector coil resistance: varies by type — commonly ~1–3 Ω for low‑impedance or ~12–16 Ω for high‑impedance injectors; consult vehicle specs
- Driver output type: typically a switched ground or switched positive depending on system
- Typical injector pulse width: 1–15 ms depending on load and RPM (varies widely with engine)
- Pulse frequency: tied to engine RPM and injector count (pulses per cylinder event)
- Expected waveform: clean square pulses with rapid transition; absence of pulses or abnormal spikes indicates fault
Diagnostic algorithm
- Connect a scan tool, record freeze frame and live data; verify P0201 and any related codes (P0301, others).
- Visually inspect injector #1 harness and connector for damage, corrosion, bent pins or water contamination; repair as needed.
- With key OFF disconnect injector connector and measure injector coil resistance across the two injector pins; compare to spec. Replace injector if open or shorted.
- With key ON measure battery voltage at the injector supply pin; verify proper fuse and power feed to injector rail.
- Backprobe the injector signal pin with a noid light or oscilloscope while cranking/starting and while engine runs; check for proper pulses and waveform shape.
- If no pulse present, trace wiring from injector to PCM: check for continuity and for short to ground or battery using a multimeter (ohms and voltage tests).
- Perform wiggle test on wiring and connectors while monitoring injector signal and engine behavior to detect intermittent faults.
- Swap injector #1 with a known good injector from another cylinder (if practical) and see if code follows the injector or stays on cylinder #1.
- If wiring and injector test good but no driver signal, suspect PCM injector driver; verify grounds, power, and perform PCM connector resistance checks before replacement.
- After repairs clear codes and test drive to confirm no return of P0201 and normal operation.
Likely causes
- Broken or chafed wire between injector #1 and ECM
- Connector terminal pushed out, corroded or contaminated
- Injector coil resistance out of specification (open or shorted)
- Injector wiring shorted to battery voltage or ground
- Failed injector driver transistor inside PCM after load stress
- Intermittent harness fault aggravated by vibration or moisture
Fault status
Status
Injector 1 Control Circuit — electrical fault detected in injector #1 control circuit (open, short, high/low circuit or driver failure).
Repair difficulty: Medium
Diagnostic time: 0.5-2.0 hours
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