Code
P20D1
Generic
P — Powertrain
Exhaust Aftertreatment Fuel Injector B Control Circuit/Open
Views:
UK: 30
EN: 32
RU: 27
AI status
Completed
Completed
100%
Causes
- Open or shorted wiring in injector B control circuit
- Corroded, damaged or loose connector at the injector or ECM
- Failed exhaust aftertreatment fuel injector B (stuck open or open coil)
- Blown fuse or bad relay supplying injector circuit power
- Faulty ECM/PCM output driver for injector B
- Poor ground or power supply to the injector circuit
Symptoms
- MIL/Check Engine lamp illuminated
- Possible reduced exhaust aftertreatment dosing efficiency or regeneration issues
- DTC P20D1 logged (may be accompanied by related aftertreatment codes)
- Possible engine derate or limited performance if the system detects critical aftertreatment failure
- No audible click from injector B when system commands dosing
What to check
- Read and record stored codes and freeze frame data (scan tool)
- Visually inspect injector B, connector, and wiring harness for damage, corrosion, pins pushed out, or water intrusion
- Inspect/verify related fuses and relays for injector power
- Backprobe injector connector and check for battery supply voltage with ignition ON (if circuit uses switched power)
- Measure injector coil resistance across injector B pins and compare to specification
- Backprobe/control side of injector while commanding injector or during cranking to verify PCM pulse (use oscilloscope if available)
Signal parameters
- Injector coil resistance (typical range, vehicle dependent): ~2–20 ohms (measure cold)
- Connector supply voltage (ignition ON, vehicle dependent): ~12 V to supply terminal (if injector uses switched power)
- Control driver output: pulsed ground or supply depending on design, 0–12 V PWM when commanded
- Pulse width/duty cycle: varies by system and operating condition (often short pulses for dosing events)
- Command current when energized: typically up to several amps momentarily (use appropriate tools)
- Expected behavior: when commanded, driver should produce consistent pulsed waveform; open circuit shows no pulses or zero current
Diagnostic algorithm
- Confirm DTC P20D1 with a scan tool and record freeze frame/live data. Check for other related codes and pending counts.
- Perform a visual inspection of injector B connector and wiring for damage, corrosion, pin push-out, or contamination. Repair/clean as needed.
- Verify power/fuse/relay feeding the injector circuit (with ignition ON). Replace any blown fuse or faulty relay and re-test.
- Disconnect the injector connector and measure injector coil resistance across its terminals; compare to specification. Replace injector if coil is open or out of spec.
- Backprobe the injector control circuit at the connector while commanding the injector or during cranking. Use a digital scope if available to look for a pulsed waveform. If no pulse, test wiring continuity to the ECM.
- Check continuity/resistance between the injector control pin and the corresponding ECM pin; inspect for shorts to ground or battery. Repair any harness faults.
- Perform a wiggle test of harness/connectors while monitoring the circuit for intermittent faults. Repair/secure any movement-causing issues.
- If available and safe, swap injector B with another same-type injector and clear codes. If the fault follows the injector, replace the injector. If the fault remains on circuit B, suspect wiring or ECM.
- If wiring and injector check good but no proper ECM output, test or replace the ECM driver only after confirming all circuit repairs and power/ground integrity.
- After repairs, clear codes, perform a relearn/regeneration procedure if required by manufacturer, then road test and verify no return of DTC.
- Document repair and retest to ensure aftertreatment dosing functions correctly and no related codes appear.
Likely causes
- Broken or chafed wire between injector B and the ECM (open circuit)
- Injector B connector pins corroded or pushed out
- Injector coil internal open or high resistance
- Battery/fuse/relay providing power to the injector is open or intermittent
- ECM driver transistor for injector B has failed (no pulse output)
- Short to ground on the control pulse wire preventing proper driver operation
Fault status
Status
Control module detected open/low current or no command to Exhaust Aftertreatment Fuel Injector B circuit (circuit open or driver fault).
Repair difficulty: Medium
Diagnostic time: 1.5 - 3.0 hours
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