Question about 2003 Volkswagen Jetta TDI
Brought the car to a local repair shop to get my O2 sensor installed (previous code). After the repair, I get this code indicating a lean condition.
The shop checked for vacuum leaks, fuel pressure, and O2 sensor operation. All of them appear to be fine. The car seems to run fine. Fuel economy is a bit low side. They are suggesting a fuel injector clean but seem unsure if it will fix the problem.
This is starting to get expensive and frustrating fast. Any insight would be great. Please don't copy the OBD trouble code info. Already have it.
Not sure that the O2 sensor was bad. It sounds like it was telling you that side of the exhaust system was picking up a lean mixure at the O2 sensor. The O2 sensor was doing its job by telling you the mixture changed. If the O2 sensor was bad, it would say low voltage range for that sensor, or open curcuit.
Now the car has had time to do its diagnostic sweep, it is telling you the same thing, but from a different sensor...the fuel mix is too lean. Air/spark/and fuel is what you need in the correct amounts. In your car, the ECM engine control module controls this by taking readings from all the sensors several hundred times a second.
Mechanically, you have a few options. Change the fuel filter...under the car on the passenger side. It is an easy job.
Change the fuel pressure regulator. This keeps the fuel at 4 BAR so the fuel injectors can do their job correctly. This job just needs a screw driver to pop off the clip that holds it in place. No hoses need to be removed. It is on top of the intake manifold, in-line with a metal fuel line and a rubber one.
The fuel injectors could be clogged up on one side of the engine. Run some fuel injector cleaner through a tank of gas. Also, listen for a constant ticking sound at each injector. If one sounds off PAR, then replace it.
The fuel pump may not be giving you enough power. However, the readings seem to be localized to one side, so I doubt it.
Start with the easiest thing, and see if it works. Also, you will need to get yourself a VAG scan tool. It is the only one with codes in it for all of your VW systems, not just engine codes like the ODB scanners. You can get a nice one for $50 on-line.
Posted on Feb 24, 2010
Here are the test procedure for a PO171 code.
1. Check and verify there are no vacuum leaks or unmetered air leaks.
2. Check and verify air filter, all inlet screens and throttle body are clear and clean (never use an aerosol cleaner to clean a throttle body, damage to the throttle body electronics may result. Use a rag dampened with cleaner to wipe the throttle clean)
3. Check and verify fuel pressure is 36 PSI at idle with vacuum to the fuel pressure regulator.
4. Check Mass Airflow Sensor (MAF) Grams/Second (G/S) readings as follows:
Idle (about 830 RPM) 3.5 G/S or more (4 to 4.5 G/S preferred).
2500 RPM no load, 9 to 15 G/S (11 to 12 G/S preferred).
Wide Open Throttle (WOT) road load (drive vehicle at 45 MPH in 3rd gear and perform a WOT acceleration, observe maximum indicated MAF G/S readings) 90 or more G/S should be present, (prefer above 100 G/S).
A MAF that exhibits consistently lower than normal G/S readings can cause a P0171 code to set. Please let me know if this information is helpful. Positive feedback is appreciated. Thank You!
Posted on Mar 21, 2009
Double check the very small hose that comes off of the manifold, since it sits so close to the manifold, I would not be surprised to find it frail and broken.
If you have tried everything else, have you had the code cleared after you changed out the parts? try having it cleared again....
Posted on Aug 21, 2009
SOURCE: 1995 jetta 2.0 fuel pump
ok could be a few things.
Have you changed the inline fuel filter? these usually have paper filter elements and after a while can be clogged with moisture which blocks fuel flow. The fuel pump will still have good pressure but the fuel rail will lack the flow required and you may burn out an injector as its running too lean. Secondly, the MAF sensor, could be dirty, clean it with electrical cleaner.
I think its more likeylt the fuel filter blocked. Try and bypass it if possible, reset the ECU and try agiain
Posted on Mar 06, 2010
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This code is related to the oxygen sensor on the drivers side of the vehicle. Most times the sensor just needs to be replaced. If you want to make sure, it is the sensor and not a wiring problem or another condition causing this you would need to preform the following test.
Monitor the bank 2 oxygen sensor (O2) voltage on the scanner. If it's showing lean (under 0.5 V), force the engine rich using some propane or carburetor spray. The O2 should go to 0.8-0.9 V.
If the O2 does not go rich as it should, check the voltage at the O2 sensor on the Black (BK) wire. Perform the same test adding external fuel. If the O2 shows rich when using a voltmeter, re-check at pin 44 Red/Black (RD/BK) wire at the Powertrain Control Module (PCM).
If the voltage at the PCM is low as the scanner shows, but the voltage at the sensor responds and goes rich, locate and repair the open circuit in between the PCM and O2 sensor connector.
If the voltage is stuck lean at the O2 and PCM using a voltmeter, cut the BK wire at the O2 sensor leaving all other wires connected. Re-check the voltage on the BK wire. If it now goes rich when adding fuel, check the RD/BK wire for any continuity to ground and repair the wire as needed.
If the wires test out OK and the O2 sensor does not switch as it should, replace the O2 sensor and retest.
Hope this helps.
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