P2149 Fuel Injector Group B Supply Voltage Circuit/Open — Causes & Fix
Updated for 2026 diagnostics & repair guidance
P2149 at a Glance
What it means
The ECU has detected a voltage fault in the supply circuit for fuel injector group B (typically cylinders 3 and 4 on a 4-cylinder, or cylinders 4–6 on a 6-cylinder).
Most common cause
Damaged wiring harness, corroded connectors, or failed injector(s) in group B.
Severity
Serious — affected cylinders will not fire correctly.
Can you drive?
Short distances only. The engine will run rough on fewer cylinders.
Typical repair cost
£40–£350 depending on wiring vs. injector replacement.
What Does P2149 Mean?
P2149 indicates the ECU has detected an open circuit or voltage fault in the power supply to fuel injector group B. Modern diesel ECUs group injectors into banks (Group A and Group B) for power management. When the supply voltage to group B is lost or abnormal, the ECU cannot fire those injectors properly, causing the engine to run on half its cylinders.
Common Causes
Injector-Related Causes
Failed injector(s) in group B
A short-circuit inside an injector solenoid can pull down the entire group's supply voltage, triggering P2149.
Other Possible Causes
Damaged injector wiring harness
Heat, vibration, or rodent damage to the wiring between the ECU and injector group B. Common in the engine bay near exhaust components.
Corroded injector connectors
Water ingress into injector connectors causes high resistance or open circuits in the group B supply.
ECU power driver failure
The transistor bank in the ECU that powers group B injectors has failed. Less common but requires ECU repair.
Aftermarket wiring modification
Poorly executed repairs or aftermarket installations can damage the injector supply circuit.
Symptoms Drivers Notice
- Engine running on half cylinders (very rough idle)
- Severe vibration through the vehicle
- Major loss of power
- Engine management light illuminated (often flashing)
- Black smoke from exhaust
- Engine may stall at idle
- DPF warning light due to incomplete combustion
Vehicles Commonly Affected
Can You Still Drive with P2149?
Driving should be limited to reaching a workshop. The engine is running on approximately half its cylinders, which means severe vibration, minimal power, and rapid DPF contamination. A flashing engine light with P2149 means stop driving immediately.
How Mechanics Diagnose P2149
- 1
Read and confirm fault codes
Confirm P2149 and check for companion codes (P2146 for group A, or individual cylinder codes P0201–P0208).
- 2
Inspect wiring harness to group B injectors
Visually check the wiring from ECU to the affected injector bank for damage, chafing, or burns.
- 3
Measure supply voltage at injector connectors
With ignition on, check for 12V supply at each group B injector connector. No voltage confirms a wiring or ECU fault.
- 4
Test individual injector resistance
Disconnect each group B injector and measure solenoid resistance. A short-circuit (near 0 ohms) identifies a failed injector pulling down the group.
- 5
Isolate and swap test
Disconnect each group B injector one at a time. If removing one restores voltage to the others, that injector has an internal short.
Repair Solutions & Costs
Repair or replace wiring harness
If wiring damage is found, repair the affected section with proper soldering and heat-shrink. Full harness replacement for severe damage.
Replace failed injector(s)
If an injector has an internal short-circuit, replacement is the only fix. Remanufactured injectors are a cost-effective, OEM-spec option.
Clean or replace connectors
Corroded connectors can be cleaned with electrical contact cleaner or replaced if severely damaged.
ECU repair
If the ECU power driver has failed, specialist ECU repair or replacement is needed.
Replacing injectors? Browse our remanufactured diesel injectors, reconditioned injectors or refurbished diesel injectors — all bench-tested with a 12-month warranty.
When Injector Replacement Is Required
Injector replacement is needed when an individual injector's solenoid resistance is out of spec (typically <0.1 ohms indicates a short circuit). The failed injector pulls down the entire group B supply voltage.
Compatible Remanufactured Injectors
OEM bench-tested injectors for engines affected by P2149 — verified pricing, 12-month warranty, free UK delivery.
Siemens VDO / Continental A2C9303500080
2.0L EcoBlue Remanufactured Common Rail Injector (Ford Transit / Transit Custom / Tourneo Custom)
Fits: ADBC, ADBD, ADBE, BC2X
View injector
Siemens VDO / Continental 5WS40156Z
DW10 / 2.0 HDi / 2.0 TDCi / D4204T Remanufactured Common Rail Injector
Fits: AZWA, AZWC, D4204T, D4204T2
View injector
Bosch 0445117021
3.0L V6 TDI Remanufactured Common Rail Injector (Audi/VW/Porsche EA897)
Fits: CJGA, CJGC, CJGD, CJMA
View injector
Bosch 0445116030
Remanufactured Bosch 0445116030 diesel injector for VAG 2.0 TDI EA189 common rail applications. Direct replacement for VW Golf, Passat, Tiguan, Audi A3, A4, A5, A6, Q5, Skoda Octavia, Superb and Seat Leon with CBAB, CAGA, CAHA and CMEA engine variants. Cross-references 0445116029, 0445116004, 0986435360, 03L130277. OEM-tested and calibrated with full flow and leak-back verification on CR318 PRO test bench. Includes 12-month unlimited-mileage warranty. Supplied as an exchange unit — return your old injector within 30 days.
Fits: CAGA, CAGB, CAGC, CAHA
View injector
Delphi 28388960
Remanufactured Delphi 28388960 diesel injector for Ford 2.0 TDCi and Peugeot/Citroen 2.0 HDi/BlueHDi DW10 engines. Direct replacement for Ford Mondeo, Kuga, S-Max, Galaxy, Focus, C-Max, Edge and Peugeot 308, 508, 3008, 5008, Expert, Citroen C4, C5, DS4, DS5, Jumpy, Jumper applications. Cross-references 28602948, 9674984080, DS7Q9F593BA, HRD360. OEM-tested and calibrated with full flow and leak-back verification. Includes 12-month unlimited-mileage warranty. Supplied as an exchange unit — return your old injector within 30 days.
Fits: AZBA, AZBC, DW10CB, DW10CTED4
View injector
Delphi 28565336
Delphi diesel injector for VW/Audi/Seat/Skoda EA288 2.0 TDI platform
Fits: CLHB, CRKB, CXXA, CXXB
View injector
Bosch 0445116022
Bosch 0445116022 remanufactured piezo common-rail diesel injector for the Volkswagen Group 3.0 V6 TDI engine (OE 059130277BE) — Audi A4/A5/A6/A7/Q5/Q7, VW Touareg and Porsche Cayenne. Professionally tested and calibrated to OEM specification. Includes: OEM Tested, 12 Month Warranty, Free UK Delivery.
Fits: CAMA, CAMB, CAPA, CASA
View injector
Bosch 0445116035
Remanufactured Bosch 0445116035 piezo common-rail diesel injector for VW Transporter T5, Multivan, California and Amarok 2.0 TDI / 2.0 BiTDI (CAAC, CFCA, CDCA, CCHA/CCHB and related engine variants). Direct replacement for VW OE 03L130277C / 03L130855BX and Bosch cross-references 0445116034, 0445116057, 0445116058, 0986435369. OEM-tested and calibrated with full flow and leak-back verification on CR318 PRO test bench. Includes 12-month unlimited-mileage warranty. Supplied as an exchange unit — return your old injector within 30 days.
Fits: CAAC, CAAD, CAAE, CCHA
View injectorCompatible Injector Part Numbers
16 injectors compatible with engines affected by P2149.
5WS40156-Z
Siemens VDO / Continental · from £90.00
3294238468
Bosch · from £90.00
0987654567
Bosch · from £99.88
765C591356
Bosch · from £100.00
0867673265
Bosch · from £100.00
32475294386
Bosch · from £100.00
8923423466
Siemens · from £100.00
100054325
Bosch · from £100.00
A6510704987
Delphi · from £100.00
664378392
Siemens · from £100.00
28307309
Delphi · from £100.00
0445110613
Bosch · from £100.00
Cross Reference Numbers
OEM and alternative part numbers for injectors affected by P2149.
Affected Vehicle & Engine Combinations
Trusted Injector Families for These Engines
Verified remanufactured injector families fitted to engines documented to log P2149.
A2C9303500080
Siemens VDO / Continental · 2.0L EcoBlue
Engines: ADBC, ADBD, ADBE, BC2X, BCCC, BCCD
5WS40156Z
Siemens VDO / Continental · DW10 / 2.0 HDi / 2.0 TDCi / D4204T
Engines: AZWA, AZWC, D4204T, D4204T2, D4204T5, DW10BTED4
0445117021
Bosch · 3.0L V6 TDI
Engines: CJGA, CJGC, CJGD, CJMA, CKVD, CLAA
0445116030
Bosch · 2.0L TDI CR (EA189)
Engines: CAGA, CAGB, CAGC, CAHA, CAHB, CBAA
28388960
Delphi · 2.0L HDi
Engines: AZBA, AZBC, DW10CB, DW10CTED4, KLBA, LPBA
28565336
Delphi · VW/Audi/Seat/Skoda 2.0 TDI (EA288)
Engines: CLHB, CRKB, CXXA, CXXB, DBKA, DDYA
Need a Replacement Injector?
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Frequently Asked Questions
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Fault Codes
Why It Happens
Common-rail injectors live at extreme pressures with clearances measured in microns. Fuel quality, heat cycles and mileage wear the internal control valve and nozzle: back-leak rises, spray patterns deteriorate and delivery drifts from calibration. Most 'engine' complaints on high-mileage diesels trace back to this gradual injector wear.
Professional Diagnosis
Workshops follow a fixed order: scan for codes and freeze-frame data, compare requested vs actual rail pressure on live data, read cylinder balance corrections, then run a comparative leak-off test. That sequence identifies the faulty injector without guesswork — and prevents needlessly replacing pumps, sensors or the wrong injector.
Typical Workshop Findings
The most frequent findings are: one injector returning several times the leak-off volume of its neighbours; carbon build-up from a failed copper washer; corroded injector connectors; and missing injector coding after a previous repair. Genuine high-pressure pump failures are rarer than back-leak faults that mimic them.
When to Replace Injectors
Replace when testing proves internal wear: leak-off clearly above the other injectors, balance corrections at their limits, or a failed bench test. Cleaning and additives cannot restore worn internal clearances. Bench-tested remanufactured injectors restore original calibration at a fraction of the new price — always coded to the ECU where the engine requires it.
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