P21E6

Code

Generic P — Powertrain

Cylinder 6 Injector B Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 16 EN: 27 RU: 24

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Page language: EN

Causes

Short to ground in the injector wiring for cylinder 6 (Injector B)
Corroded/damaged or loose connector at the injector
Failed or internally shorted fuel injector (low resistance)
Open or high-resistance power supply or ground for the injector circuit
Faulty ECM/injector driver transistor
Blown fuse or faulty relay supplying injector power

Symptoms

Check Engine Light (MIL) illuminated
Rough idle or vibration (cylinder 6 misfire)
Poor acceleration or loss of power
Reduced fuel economy
Hard starting or stumbling at idle
Possible stored misfire code(s) for cylinder 6 (e.g., P0306)

What to check

Read and record freeze-frame data and all related codes with a scan tool
Visual inspection of injector 6 (B) connector, pins and harness for corrosion, damage or water
Check fuses and relays related to the fuel injectors and PCM power supplies
Measure injector resistance (cold) at the injector — compare to spec
Backprobe injector connector to check battery feed (key ON) and driver signal while cranking
Use a noid light or oscilloscope to verify injector pulse pattern and amplitude

Signal parameters

Injector supply (battery side): ≈ 11–14 V with key ON (varies by vehicle)
Injector terminal resistance: commonly low (1–16 Ω) depending on type — check OEM spec
Driver output: low-side switching to ground when commanded; voltage will pulse between near battery voltage and near 0 V
Injector current when energized: typically 1–6 A for gasoline injectors; diesel/solenoid types vary — consult OEM data
No injector pulse (stuck low) or permanently low voltage at driver indicates short to ground or driver failure

Diagnostic algorithm

Retrieve all DTCs and freeze-frame data; note related codes (misfire, low voltage, supply faults).
Visually inspect wiring, harness routing and the cylinder 6 injector connector for damage, corrosion or water intrusion.
With key ON (engine OFF) measure voltage at the injector’s battery feed terminal — should be near battery voltage. If absent, trace fuses/relays/power feeds.
Measure injector coil resistance at the connector (engine OFF). If resistance is significantly lower than spec, the injector may be shorted.
Backprobe the connector while cranking or running: observe the driver pin. Use a noid light or oscilloscope to confirm the injector is being pulsed. If driver line reads near 0 V continuously, check for short to ground; if it never pulses, check ECM command signal.
Perform a wiggle test of wiring while observing live data to find intermittent shorts/opens.
Swap the suspect injector with another cylinder’s injector (if identical) and retest. If the DTC moves to the other cylinder, replace the injector.
If wiring and injector check OK but the circuit remains low, inspect/repair harness up to the ECM connector. If wiring is intact and connector pins are good, consider ECM driver failure and test/replace ECM per OEM procedures.
After repairs, clear codes and perform a road test to confirm no recurrence and proper engine operation.

Likely causes

Wiring short to ground between injector connector and ECM
Corroded or loose injector connector causing intermittent low voltage
Injector itself has failed and presents abnormally low resistance
ECM driver stage failed (less common than wiring/connector faults)

Fault status

⚠️ Status

P21E6 — Cylinder 6 Injector B Circuit Low: ECM detected abnormally low voltage on injector B of cylinder 6 (possible short to ground, connector/wiring fault, failed injector or ECM driver). Further diagnosis required; do not assume final cause until tested.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-2.5 hours