P02AD

Cylinder 5 - Injector Leaking

P02AD is a generic OBD-II powertrain diagnostic trouble code: Cylinder 5 - Injector Leaking. It is logged by the engine control unit when the fuel/inj monitor detects that a specific fault threshold has been exceeded — typically resulting in the malfunction-indicator lamp (MIL / check-engine light) being illuminated.

Code
P02AD
Group
Powertrain
System
Fuel/Inj
Severity
Warning (MIL on)
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What P02AD means

The P02AD code is set when the powertrain control module (PCM) detects that the fuel injector serving cylinder 5 is leaking fuel into the combustion chamber. Rather than metering a precise pulse of fuel at the correct moment, a leaking injector allows fuel to seep past its needle valve or sealing surfaces continuously, even when commanded off. The PCM infers this condition by monitoring long-term fuel trim corrections, oxygen sensor feedback, and cylinder-specific misfire counters: a leaking injector causes a locally rich mixture that forces the PCM to cut fuel delivery below its normal range. In a six- or eight-cylinder engine, cylinder 5 is typically on the passenger-side bank, and injector leakage there can wash oil from the cylinder wall, dilute engine oil with raw fuel, and produce unburned hydrocarbon emissions. Left unaddressed, persistent fuel wash causes accelerated ring and bore wear, catalytic converter overload, and in severe cases hydraulic lock at startup. The code is generic and applies to any OBD-II compliant vehicle with a port- or direct-injection system where individual cylinder fuel trims are monitored. Early repair is strongly recommended to prevent secondary mechanical damage.

Common causes

Most-frequently reported root causes when P02AD is logged.

  • 1
    Worn or cracked injector O-rings allowing fuel to seep around the injector body
  • 2
    Failed injector needle valve or internal spring that does not fully close when de-energised
  • 3
    Excessive fuel rail pressure caused by a faulty fuel pressure regulator holding pressure above spec
  • 4
    Carbon or varnish deposits on the injector tip preventing the needle from seating cleanly
  • 5
    Damaged injector pintle cap or tip cracked from heat cycling
  • 6
    Contaminated fuel introducing abrasive particles that score the injector seat
  • 7
    Corrosion at the injector body due to moisture ingress or poor-quality fuel additives

Symptoms drivers notice

MIL (Check Engine Light) illuminated with P02AD stored
Rough or lumpy idle caused by an over-rich mixture in cylinder 5
Fuel odour inside or around the engine bay from raw fuel vapour
Reduced fuel economy as excess fuel bypasses combustion
Cylinder 5 misfire codes (P0305) may accompany P02AD if the rich condition is severe
Engine oil diluted with fuel detectable by a fuel smell on the dipstick

How to diagnose P02AD

A typical diagnostic flow when this code is present.

  1. 1
    Connect a scan tool, record freeze-frame data, and note long-term fuel trim values for the bank containing cylinder 5
  2. 2
    Perform a fuel injector balance test using the scan tool's bidirectional controls to confirm cylinder 5 is the outlier
  3. 3
    With the engine off and fuel pressure held, remove the cylinder 5 injector and visually inspect O-rings, pintle, and tip for cracking or varnish build-up
  4. 4
    Bench-test or ultrasonic-clean the injector to measure flow rate, spray pattern, and leak-down; replace if it fails to close within spec
  5. 5
    Check fuel rail pressure with a gauge against manufacturer specification; an over-pressure condition will cause multiple injectors to weep
  6. 6
    Swap the suspect injector to another cylinder and re-run the balance test — if the fault moves with the injector, replace it
  7. 7
    Clear codes, perform a test drive, and verify fuel trims return to within ±10% before closing the repair

Related powertrain codes

Frequently asked questions

Can I keep driving with a P02AD code active?

Short-term driving is possible, but it is not advisable. Continuous fuel leakage washes lubricant from the cylinder wall, dilutes the engine oil, and overloads the catalytic converter. Repair should be carried out promptly to avoid escalating mechanical damage.

Will cleaning the injector fix a P02AD leak?

If the leak is caused by varnish deposits preventing the needle from seating, professional ultrasonic cleaning may restore proper closure. However, if the O-ring, needle seat, or pintle is physically damaged, the injector must be replaced.

Could a bad fuel pressure regulator cause P02AD on just one cylinder?

A faulty regulator that holds excessive pressure can cause the weakest injector in the rail to weep first, which may initially appear as a single-cylinder fault. Testing fuel rail pressure is an important step before condemning the injector alone.

How is P02AD different from a P0305 misfire code?

P0305 indicates cylinder 5 is misfiring without identifying why; P02AD specifically indicates the PCM has traced the fault to injector leakage. Both codes can coexist when a severe rich condition quenches combustion in that cylinder.

Disabling P02AD in software

RaceTune can permanently disable P02AD — and any other OBD-II diagnostic trouble code — on every ECU family we support. The monitor is disabled inside the ECU itself, so the fault stops being logged: the warning light stays off and the engine never enters limp mode for this code. The change is tied to your exact software version.

Permanent
The monitor is disabled in the ECU itself — not just cleared. It cannot return.
Tailored to your file
Each patch is matched to your specific software version — never a one-size-fits-all file.
Reversible
The original file is always preserved. Reflash the stock to return the ECU to factory state.

Software modifications affect emissions compliance and are not road-legal in many jurisdictions. RaceTune service files are intended for motorsport, off-road, and export use.

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