Good day all-
2000 VR6, 175k miles, drives great. CEL came on and the only code present:
P1136, Long Term Fuel Trim Add. Fuel B1 System Too Lean. I have scoured this forum for a concise meaning of the code description and really can't figure out the definition. I am new to OBD auto systems but I have extensive auto experience with older VW's. As a starting point, I would like some confirmation on my diagnosis and method to proceed.

Fuel B1 System too lean: Motor is running (tending to) rich and the computer trims fuel causing a lean condition (according to the computer).

Causes:
Vacuum leak...check replace hoses
Fuel filter? Fuel injectors? No noticeable drivability issues
MAF sensor degraded...clean and/or replace
O2 Sensor(s) can these be removed and cleaned/reinstalled?

Any other thoughts are certainly welcome. Great forum.

TIA Kevin

 

Clean the maff sensor and you throttle body. Check the air intake boot and any other vacuum hoses for leaks.
Let me know how it goes...

 

Thanks for the reply. OK, removed MAF, cleaned throttle body and MAF and all associated parts. Looked pretty clean to begin with. The same code flashed within a few miles. Took it to my mechanic who (for free) plugged it in to the BIG code reader. Same code and engine fuel/air reads normal in all engine rpm ranges (car drives great). The only thing we did not do is a tap test on the MAF while running. I want to stop short of just slapping on a new sensor. They're not cheap. Is there a test procedure to verify the continuity in the wiring harness to the sensor?? There are 5 terminals and I have a digital multi meter I am very comfortable using. Anyone have a schematic to make a test harness for the MAF to verify its function??? Seems this problem comes up often...chasing codes...and if we can help others at my expense we come out ahead. Thanks again.


Kevin

 

Mass Air Flow (MAF) Sensor, Checking

NOTE: Use only gold-plated terminals when servicing terminals in harness connector of Mass Air Flow (MAF) sensor.

Recommended special tools and equipment

• VAG1526 multimeter or VAG1715 multimeter
• VAG1594 connector test kit
• Wiring diagram

Test requirements

• The respective fuses of Mass Air Flow (MAF) Sensor -G70- must be OK.
• Fuel Pump (FP) Relay -J17- must be OK, check:
• Battery voltage must be at least 11.5 volts.
• All electrical consumers like, for example, lights and rear window heating must be switched off.
• Parking brake must be engaged or else daylight driving lights will be switched on.
• For vehicles with automatic transmission, selector lever must be in position -P- or -N-.
• If vehicle is equipped with an A/C system, it must be switched off.
• Ground (GND) connections between engine and chassis must be OK.
• Coolant temperature must be at least 80 degree C , Diagnostic mode 1: Check measuring values; PID 5, Coolant temperature.

See: Testing and Inspection\Scan Tool Testing and Procedures\With Generic Scan Tool\Diagnostic Mode 1: Check Measured Values

Function test

• Connect diagnostic tester.

See: Testing and Inspection\Reading and Clearing Diagnostic Trouble Codes\Scan Tool Connecting\With Generic Scan Tool\Diagnostic Tester, Connecting

• Start engine and let run at idle.
• Under address word 33, select "Diagnostic mode 1: Checking measured values."
• Select the measuring value "PID 16: Air flow quantity at Mass Air Flow (MAF) sensor".
• Check specified value of air flow quantity at Mass Air Flow (MAF) Sensor at idle. Specified value: 3.00 to 5.00 g/sec
• End diagnosis and switch ignition off.

If specified value is obtained, but DTC memory has a DTC concerning Mass Air Flow (MAF) sensor:

• Check voltage supply of Mass Air Flow (MAF) sensor.

If specified value is not obtained:

• Check signal and Ground (GND) wires of Mass Air Flow (MAF) sensor.

Voltage supply for Mass Air Flow (MAF) sensor, checking

• Disconnect 5-pin connector from Mass Air Flow (MAF) Sensor -G70- with Intake Air Temperature (IAT) Sensor -G42- (arrow).

• Connect multimeter to terminal 2 of connector and engine Ground (GND) for voltage measurement.
• Start engine, and let run at idle. Specified value: 11.0 to 15.0 V
• Switch ignition off.

If there is no voltage:

• Check wire between 5-pin connector terminal 2 and the Fuel Pump (FP) Relay -J17- for open circuit according to wiring diagram. Wire resistance: max: 1.5 Ohm

If voltage supply and wires are OK:

• Connect multimeter to terminal 4 of connector and engine Ground (GND) for voltage measurement.
• Switch ignition on.
• Specified value: at least 4.5 V Switch ignition off.

If there is no voltage:

• Check signal and Ground (GND) wire of Mass Air Flow (MAF) sensor.

Checking signal and Ground wires of Mass Air Flow (MAF) Sensor

• Connect test box to control module wiring harness, connect test box for wiring test.

See: Testing and Inspection\Reading and Clearing Diagnostic Trouble Codes\Scan Tool Connecting\With Generic Scan Tool\Test Box, Connecting For Wiring Test

• Check wires between test box and 5-pin connector for open circuit according to wiring diagram. Terminal 3 + socket 27

Terminal 4 + socket 53
Terminal 5 + socket 29
Wire resistance: max: 1.5 Ohm

• Also check wires for short circuit to each other, to vehicle Ground (GND) and to B+. Specified value: infinite Ohm

If no DTCs are found in wires:

• Replace Mass Air Flow (MAF) Sensor -G70-:
• Vehicles with engine code AFP, item 4 ,
• Vehicles with engine code BDF, item 6 .
• Erase DTC memory of Engine Control Module (ECM), Diagnostic mode 4: Reset/erase diagnostic data.

See: Testing and Inspection\Scan Tool Testing and Procedures\With Generic Scan Tool\Diagnostic Mode 4: Reset/Erase Diagnostic Data

• Generate readiness code.

See: Testing and Inspection\Monitors, Trips, Drive Cycles and Readiness Codes

 

let me know if that helps man.

 

Nice...
I'll check it out when I get the time away from work. Thanks much!!!