P0172

System Too Rich (Bank 1)

Symptoms

• •Black smoke
• •Poor economy
• •Rough running

Likely causes

• •Leaking injector
• •Faulty MAF/MAP sensor
• •High fuel pressure
• •Dirty air filter

Can I drive?

Diagnose soon.

Estimated repair cost (Malaysia)

RM200–RM800 (approximate)

Diagnostic guide (for mechanics)

Work through these in order — cheapest and safest checks first, before replacing expensive parts.

1. 1. Read fuel trims to confirm rich

   Confirm a rich condition and whether it is worse at idle or load.

   Test: Live data short/long-term fuel trim bank 1.

   Expected: Rich = strongly negative trims (well below -10%).

2. 2. Check for raw fuel / leaking injector

   A leaking injector or high fuel pressure dumps excess fuel.

   Test: Inspect plugs for fuel fouling; check fuel pressure.

   Expected: Pressure to spec; plugs not wet/black.

3. 3. Inspect MAF over-reading and intake

   An over-reporting MAF or restricted air (dirty filter) can drive rich.

   Test: Live data MAF plausibility; inspect air filter.

   Expected: Plausible airflow; clean filter.

Tools: OBD-II scan tool · Fuel-pressure gauge

When to escalate: If trims stay rich after fuel pressure, injectors and MAF check out, refer for deeper fuel-control diagnosis.

This is general information, not a diagnosis. AutoMalaya OBD helps explain your car’s actual scan data; a qualified mechanic may still need to inspect the vehicle.

Related fault codes

See sample report