Volkswagen P1137 Code Meaning
At idle the VW computer is pulling out as much fuel as it's allowed on bank 1 and the mix is still too rich.
Safety first · Consult a professional
- Fuel vapor is flammable. No smoking or open flames; work outdoors and fix fuel leaks before driving.
At a glance
Severity: Low
- Meaning
- Fuel Trim Bank 1 (Additive) System Too Rich – Idle
- System
- Fuel & Air Metering · Powertrain
- Safe to drive?
- Yes, short term
- Typical repair cost
- $50–$650
- DIY difficulty
- Moderate
P1137, shown by VCDS as 17545 'Fuel Trim: Bank 1 (Add): System too Rich', is the mirror image of P1136: the additive (idle) fuel correction has reached its negative limit. The ECU keeps shortening injector on-time at idle because extra fuel is arriving from somewhere it doesn't control. On Mk4-era VWs the usual sources are fuel vapor from a purge valve stuck open or a flooded charcoal canister, injectors that drip after shut-off, a leaking fuel pressure regulator diaphragm, or fuel-diluted oil feeding vapor through the PCV system. Because these sources are fixed amounts, they dominate at idle and fade as rpm rises.
Can I keep driving? It's usually safe to drive, but a strong raw-fuel smell or a leaking injector is a fire risk – park it and have it checked. A long-running rich idle also loads the catalytic converter.
How to read P1137
- P Powertrain
- 1 Manufacturer-specific
- 1 Fuel & air metering
- 37 Specific fault
Symptoms
- Check engine light with P1137 (VCDS 17545) stored
- Slightly rough idle or rpm dip right after a hot restart
- Raw fuel smell, especially after filling the tank
- Long cranking when restarting a hot engine
- Sooty tailpipe or rotten-egg smell from the exhaust
Possible causes
Ranked by how often each cause is behind this code (editorial estimate).
- EVAP purge valve (N80) stuck open or charcoal canister flooded from topping off the tank
- Injectors dripping or not sealing after shut-off
- Fuel pressure regulator diaphragm leaking or its vacuum hose off, raising pressure
- Engine oil diluted with fuel (lots of short cold trips) sending vapor through the PCV
- Front O2 sensor contaminated or biased, reporting a false rich reading
- MAF sensor over-reading at low airflow
Diagnosis step by step
Confirm the trim pattern
On a warm engine read VCDS block 032: field 1 (additive) deep negative with field 2 near zero confirms an idle-dominant rich source. If both fields are strongly negative, look harder at fuel pressure and the O2 sensor.
Tools: OBD-II scanner
Isolate the purge system
At idle, pinch or disconnect and cap the purge line between the N80 valve and the intake. If the live O2 correction swings back toward normal within a minute, the purge valve is leaking or the canister is saturated with liquid fuel.
Tools: Pliers, OBD-II scanner
Check the regulator vacuum hose for fuel
Pull the vacuum hose off the fuel pressure regulator with the engine running. Any fuel in or dripping from the hose means the diaphragm has failed and fuel is being sucked straight into the intake.
Tools: Flashlight
Test fuel pressure hold
With a gauge on the rail, run the pump, shut off and watch pressure for 10 minutes. A rapid drop with no external leak points to leaking injectors or a check valve; injectors can then be flow- and leak-tested off the car.
Tools: Fuel pressure gauge
Smell the oil
Pull the dipstick and smell it. Oil that smells strongly of gasoline or is above the full mark after many short trips will feed fuel vapor into the intake; an oil change plus a longer highway drive often makes the trim recover.
Evaluate the front O2 sensor
Snap the throttle and watch the front sensor: it should drop below about 0.2 V on decel and rise above 0.8 V on acceleration quickly. A lazy or silicone-contaminated sensor can make the ECU believe the mix is rich.
Tools: OBD-II scanner
Where the parts are
- 1Gas cap
- 2Charcoal canister
- 3Purge valve
- 4Vent valve
- 5Fuel pump
- 6Intake manifold
Repair options & costs
| Repair | DIY? | Estimated cost |
|---|---|---|
| Replace EVAP purge valve (N80) | Yes | $60–$200 |
| Replace charcoal canister | No | $180–$450 |
| Replace fuel pressure regulator | Yes | $70–$220 |
| Replace or recondition leaking injectors | No | $200–$650 |
| Oil change to remove fuel dilution | Yes | $50–$110 |
Rough US estimates for parts and labor; shop rates vary by region. Not a quote.
Notes by brand
Audi
The same 17545/P1137 appears on the A4 B5/B6 1.8T; its purge valve sits near the intake and a sticking valve is a frequent cause there too.
Emissions / smog test impact
Will fail
With the check engine light on, the car fails the OBD-II emissions test. A rich idle can also push CO and HC high in states that still run a tailpipe test.
Frequently asked questions
Why only at idle?
The 'Add' in the fault name means the additive correction, which is a fixed amount of fuel. A small uncontrolled fuel source such as vapor or a dripping injector is significant at idle and becomes negligible at higher rpm.
Can topping off the gas tank cause P1137?
Yes. Clicking the nozzle several extra times can push liquid fuel into the charcoal canister, and the purge system then feeds rich vapor into the intake. The canister may need replacing if it's soaked.
How does VCDS show this code?
Typically as '17545 – Fuel Trim: Bank 1 (Add): System too Rich, P1137 – 35-10 – Intermittent'. Ross-Tech lists it as 17545/P1137/004407.
Is P1137 the same as P0172?
Both mean a rich condition, but P0172 is the generic code from the total trim. P1137 tells you specifically that the idle part of the correction is at its limit, which narrows the search to vapor and leak-down sources.
Sources
- Manufacturer public service information (cross-checked)
- Methodology: How We Build Code Pages · Data Sources We Use · Editorial Policy