Vauxhall A20DTH 2.0 CDTi Injector Problems: Symptoms & Repair (UK)

The A20DTH replaced the Z19DTH as Vauxhall's mainstream diesel. Found in the Insignia, Astra J, and Zafira Tourer. Uses Bosch solenoid injectors. The 163hp version is the most common in the UK.

Common A20DTH injector failure symptoms

• Rough idle: Injector imbalance creates vibration at idle.
• DPF regeneration issues: Poor combustion accelerates DPF soot loading.
• Engine management light: Injector and emissions-related codes.

Why A20DTH injectors fail

• fuel contamination
• high-pressure wear cycles
• carbon buildup
• poor fuel quality
• internal valve wear

How to diagnose A20DTH injector faults

1. Read fault codes: Connect an OBD-II scanner and note any injector-related codes (P0201–P0204, P2146, P2149). This identifies which cylinder is affected.
2. Perform a leak-off test: Disconnect the fuel return pipes and route into measuring containers. Run the engine at idle for 60 seconds. Compare volumes per cylinder against manufacturer spec.
3. Listen for injector tick: Use a mechanic's stethoscope on each injector body. A dead or irregular tick indicates a stuck or failing solenoid.
4. Check fuel rail pressure: Monitor live fuel rail pressure data via diagnostic tool. Low pressure can mimic injector symptoms and may indicate a fuel pump issue instead.
5. Inspect for external leaks: Check around injector seals for signs of fuel or combustion gas leakage. Black carbon deposits indicate a blown seal.
6. Cylinder balance test: Use diagnostic software to run a cylinder contribution test. This electronically disables each injector in turn to measure its effect on engine speed.

Fault codes linked to A20DTH injector issues

• P0201-P0204 – Injector circuit malfunction
• P2002 – DPF efficiency below threshold

A20DTH repair advice

A20DTH injectors require IMA coding via GDS2/MDI. Check DPF condition after injector replacement.

A20DTH injector replacement cost (UK)

• Per injector: £180 - £350
• Full set: £700 - £1,200
• Labour: £120 - £300

Compatible injector part numbers for A20DTH

• Bosch 0445110423 – Bosch injector for A20DTH
• Vauxhall 55577668 – Vauxhall OE reference

Vehicles using the A20DTH engine

• Vauxhall Insignia (2008-2017)
• Vauxhall Astra J (2009-2015)
• Vauxhall Zafira Tourer (2011-2018)

Find your exact A20DTH injector by registration

Frequently asked questions

How much does A20DTH injector replacement cost?

A set of four costs £400-£700. Labour is 2-3 hours.

Do A20DTH injectors need coding?

Yes. IMA coding via GDS2 or compatible tool is mandatory.

How much does it cost to replace injectors?

Replacement typically costs £150–£350 per injector depending on brand and engine. A full set of four with professional fitting usually costs £600–£1,200.

Can I drive with a faulty injector?

Driving with a faulty injector can cause engine damage, increased fuel consumption, DPF contamination, and oil dilution. We recommend diagnosis and replacement as soon as possible.

Do new injectors need coding?

Some vehicles require injector coding after replacement using manufacturer-specific diagnostic tools. Many Bosch solenoid units are plug and play. Check your engine guide for specific requirements.