P2156

Code

Generic P — Powertrain

Fuel Injector Group D Supply Voltage Circuit Low

Brand: Generic

Type: P — Powertrain

Views: UK: 22 EN: 33 RU: 31

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Page language: EN

Causes

Blown fuse or faulty relay for injector/EFI supply
Open, short to ground or high-resistance connection in the injector group D supply wiring or connector
Corroded or loose injector harness connector(s)
Shorted or failed fuel injector(s) drawing excessive current
Faulty ECM / injector driver module
Low battery or poor charging system voltage

Symptoms

Malfunction Indicator Lamp (MIL) illuminated
Engine misfire, rough idle or hesitation under load
Hard starting or no-start condition
Reduced engine power or limp-home mode
Poor fuel economy
Intermittent faults or codes that clear and return

What to check

Read freeze-frame and live data with a scan tool; note operating conditions when code set
Visually inspect injector harness, connectors and pins for corrosion, damage or loose terminals
Check relevant fuses and fuel/injector relays for continuity and correct operation
Measure battery and charging system voltage (key ON and engine running)
Backprobe injector group D supply connector and measure supply voltage with key ON and during cranking
Check injector coil resistances to identify shorted or open injectors

Signal parameters

Expected injector supply voltage: approximately battery voltage (typically 11.5–14.5 V with key ON/engine running)
Acceptable voltage drop on supply circuit: generally
Typical fuel injector coil resistance (varies by engine): commonly ~2–16 Ω — check manufacturer spec
Injector driver outputs are low-side switching (drivers pull to ground); pulse width and frequency vary with engine load/speed
If supply is below ~9–10 V under load the ECM may set a low-supply DTC

Diagnostic algorithm

Verify code: connect a scan tool, confirm P2156 is current/persistent and note freeze-frame data and related codes.
Inspect: visually check harness, connectors, pins and grounds for corrosion, bent pins, heat damage or water intrusion at injector group D.
Power/fuse check: locate and check fuse(s) and relay(s) for the EFI/injector supply circuit; replace if faulty.
Measure supply voltage: backprobe the injector group D supply feed with key ON (engine off). Voltage should be near battery voltage. If low, trace back toward fuse/relay/battery.
Load test: with engine cranking or running, re-measure supply voltage to detect voltage drop under load.
Isolate injectors: disconnect group D injector connectors and measure supply voltage at the harness to see if a shorted injector is loading the circuit. If voltage returns to normal with injectors disconnected, inspect/replace the offending injector(s).
Check continuity: use an ohmmeter to check continuity to battery voltage and for shorts to ground on the supply circuit between the fuse/relay and injector group D connectors.
Check injector coil resistance: measure each injector's resistance against spec; replace any out-of-spec injector.
Scope test (if available): monitor supply and driver waveforms while the engine runs to detect abnormal switching or excessive current draw.
Repair wiring/connector faults or replace blown fuses/relays. If wiring and injectors test good, consider ECM/injector driver fault and consult manufacturer procedures for PCM testing/replacement.
Clear code(s) and road-test to verify repair. Re-scan for return of code or related DTCs.

Likely causes

Corroded/loose connector or damaged wiring at the injector group D harness
Blown fuse or failed EFI/injector supply relay
Short to ground on the injector supply circuit caused by damaged insulation or a failed injector
Failed injector driver inside the ECM (less common)

Fault status

⚠️ Status

ECM detected low voltage on Fuel Injector Group D supply circuit. Injector group D may be disabled or operating improperly. MIL set and driveability symptoms possible.

🟡 Repair difficulty: Medium

⏱️ Diagnostic time: 1.0-3.0 hours