P21D0

Code

Generic P — Powertrain

Cylinder 2 Injector B Circuit/Open

Brand: Generic

Type: P — Powertrain

Views: UK: 27 EN: 145 RU: 24

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Page language: EN

Causes

Open or broken wiring in the injector circuit to Cylinder 2 Injector B
Connector corrosion, bent pins or poor connection at the injector or harness
Faulty injector (open coil)
Faulty injector driver output in the PCM/ECM
Short to ground or short to battery in the injector wiring
Intermittent connection from heat, vibration or damaged insulation

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Engine misfire on cylinder 2, rough idle or vibration
Reduced engine power and poorer fuel economy
Hard start or extended crank time
Possible increased white/black exhaust smoke (diesel/gasoline variations)

What to check

Read freeze frame and live data (injector pulse width, commanded on/off, misfire counters)
Visually inspect the injector connector, wiring harness and harness routing for damage, corrosion, or pin contamination
Check for stored related misfire codes (P02xx) and cylinder-specific misfire counts
Measure injector coil resistance at the connector (engine off) and compare to manufacturer spec
Back-probe injector connector while cranking/engine running to confirm injector supply voltage and driver signal
Check continuity between injector connector and PCM pin (for open) and for short to ground or battery

Signal parameters

Injector coil resistance: typical high-impedance 12–16 Ω or low-impedance 2–4 Ω depending on system — compare to vehicle spec
Supply voltage at injector connector (constant): ~battery voltage (~11–14 V) with key ON
Driver output: pulsed switching (low-side or high-side) from the PCM — measured with a scope or DVOM showing pulsed voltage on command
Injector pulse width: varies with load/engine conditions (milliseconds) observable in live data
Current draw during activation: typically hundreds of milliamps to a few amps depending on injector type (use current probe for exact value)

Diagnostic algorithm

Retrieve freeze-frame data and related codes; note misfire counts and engine conditions when fault set.
Visually inspect cylinder 2 injector connector and adjacent wiring for damage, corrosion, rodent chew, or pin push-out. Repair any obvious damage.
With ignition OFF, disconnect injector connector and measure injector coil resistance across injector pins. Compare to manufacturer spec. If open/infinite -> replace injector.
Check for continuity between the injector harness connector and the PCM pin for that injector circuit. Confirm no opens and note resistance. Also check for short to ground or battery.
With key ON (engine off) back-probe the connector and verify supply voltage (should be battery voltage) and that the PCM driver returns are present (when commanded, you should see pulsed voltage or switching). Use a noid light or oscilloscope to confirm proper injector drive pattern.
If wiring and connector are good and injector has correct resistance, perform an injector swap with another known-good cylinder (when safe). Clear codes and run engine: if code follows the injector, replace the injector; if it remains on cylinder 2, suspect wiring/PCM.
If injector and wiring check good but no driver signal, check PCM grounds, related fuses and relays. If PCM output is absent or incorrect, consult manufacturer procedure for PCM testing/replacement.
After repairs, clear codes and road-test or reproduce conditions to confirm fault does not return. Re-scan to ensure no intermittent issues.

Likely causes

Open or damaged wiring harness or connector at Cylinder 2 injector
Injector coil has failed (high/∞ resistance)
Poor/cracked connector pin or corrosion at the injector harness
PCM driver failure (less likely after wiring and injector are confirmed good)

Fault status

⚠️ Status

P21D0 — Cylinder 2 Injector B Circuit/Open: ECM detected an open or fault in the drive circuit for Cylinder 2 Injector B (no proper injector drive or open coil). Inspect wiring, connector and injector; if wiring and connector are good, test/replace the injector or evaluate the PCM driver.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 0.5-3 hours