Code
P1137
VOLKSWAGEN
P — Powertrain
Long Term Fuel Trim Add Fuel Bank 1 System Too Rich
Views:
UK: 24
EN: 62
RU: 40
AI status
Completed
Completed
100%
Causes
- Faulty or contaminated upstream MAF or MAP sensor giving incorrect airflow readings
- Leaking or stuck-open fuel injector(s) on Bank 1
- Excessive fuel pressure (failed regulator or stuck open returnless regulator)
- Faulty oxygen (lambda) sensor(s) or oxygen sensor heater circuit providing incorrect rich bias
- Faulty coolant temperature sensor or other sensor causing over-fueling
- Open or shorted wiring / poor connector to fuel or air metering sensors
Symptoms
- Check Engine Light (MIL) illuminated
- Poor fuel economy
- Black smoke from exhaust at idle or load (in severe cases)
- Rough idle or hesitant acceleration
- Strong fuel smell from exhaust or intake
- Failed emissions/inspections
What to check
- Read freeze frame and live-data (scan tool) for LTFT, STFT, O2 voltages, MAF g/s, fuel pressure and engine temp
- Verify code relates to Bank 1 (cylinder bank orientation on engine)
- Visually inspect intake tubing, MAF connector, vacuum hoses and fuel rail for leaks
- Check fuel pressure at the rail under key-on and running conditions to compare with spec
- Inspect injector condition and wiring on Bank 1 for leaks or stuck injectors
- Check O2 sensor response and heater operation
Signal parameters
- Long Term Fuel Trim (Bank 1): out of normal range (typically larger than +/-10–20% depending on vehicle spec)
- Short Term Fuel Trim (Bank 1): showing sustained offset in same direction as LTFT
- Upstream O2 (wideband/narrowband) voltage: sustained high voltage (~0.7–1.0 V narrowband) or rich reading on wideband
- MAF mass airflow (g/s) or frequency: lower than expected for load/engine speed if under-reporting air
- Fuel rail pressure: higher than manufacturer spec or excessive rise under load
- Engine coolant temperature: lower-than-expected temp sensor reading may command enrichment
Diagnostic algorithm
- Confirm P1137 with a full scan — record freeze frame and live data (LTFT/STFT, O2 volts, MAF, fuel pressure, coolant temp).
- Clear codes and perform a road/drive cycle while monitoring fuel trims and sensor data to reproduce the fault.
- Inspect intake tract, MAF sensor and connections. Clean or replace MAF if contaminated and re-test.
- Check fuel pressure and compare to VW specification (static and under-load). Repair or replace fuel pressure regulator or fuel pump components if out of spec.
- Inspect injectors on Bank 1: perform balance/flow testing or a leak-down test. Replace or service leaking/inoperative injectors.
- Test upstream O2 sensor(s) — verify switching (narrowband) or correct lambda output (wideband); repair harness or replace sensor if faulty.
- Verify engine coolant temperature sensor readings vs actual temp; replace if it falsely indicates cold condition.
- Inspect EVAP purge valve and PCV system for stuck conditions that can affect fueling.
- Check wiring and connectors for corrosion, chafing or shorts on MAF, O2, injector circuits and fuel pressure sensor.
- If no hardware fault found, review ECU software updates and consider ECU adaptive reset (clear learned trims) then retest to confirm persistent condition.
- After repair, clear DTCs and verify repair with multiple drive cycles and re-check for code return and proper fuel trim behavior.
Likely causes
- Contaminated MAF leading to under-reporting air flow (ECU adds fuel)
- High fuel rail pressure or stuck-open regulator delivering too much fuel
- Leaking injector(s) on Bank 1 causing rich mixture
- Faulty upstream O2 sensor reporting high voltage (rich) bias to ECU
- Faulty engine coolant temperature sensor commanding richer cold-enrichment
Fault status
Status
PCM reports long-term fuel trim on Bank 1 in the 'add fuel' direction and flags the system as too rich; further diagnosis required to determine sensor or mechanical cause.
Repair difficulty: Medium
Diagnostic time: 1-3 hours
Your experience will help others
+100 karma for a short comment :)
Was this AI description helpful?
Your feedback helps improve AI descriptions.
👍 Like
0
👎 Dislike
0
Send to email