flickjo96

96 with a 300 inline six and a 5 spd. i had a check engine light on since august or so. i borrowed a scanner from a neighbor and got the PO171 and PO174 codes (lean codes, banks 1 and 2) i replaced both O2 sensors already with no change. i have a moderate exhaust leak before the sensors also. could the leak cause the codes? also, is there any possibility that a clogged fuel filter could cause the codes?

J.D.

i would change out the filter anyway if you havent changed it yet and also get the leak fixed that might help but my philosophy is always start with the cheap way out the filter might cost 20 bucks or less and the leak might be more it all depends on how bad it is

wde3477

Doggone - looks like the SAE is locking down on free distribution of codes. Guess they're wanting some additional bucks for use of their technology?

At any rate - found these definitions from: http://autorepair.about.com/cs/troub...l/bl_obd_1.htm

Hope they cut-n-paste OK - if not, I'll edit and fix it. *edit* - fixed.

P0131 O2 Sensor Circuit Low Voltage (Bank 1 Sensor 1)
P0134 O2 Sensor Circuit No Activity Detected (Bank 1 Sensor 1)

Looks like there may be a wiring or connector problem with the sensor since you've already replaced the sensor itself - the feedback is not getting to the computer as indicated by PO134.

If you had a fuel supply problem - would think it would show up in both banks. Depending on which set of code definitions you believe, a fuel supply problem is not totally out of the question, however I would think you would notice operation or performance problems along with any codes.

If in doubt - suggest that the best place to change a filter is in your garage or driveway - not along side the road. A filter on its way to plugging will do so at an increasing rate, since there is less and less area for the gas to get through as the filter fills with material.

IMO, an exhaust leak shouldn't cause the problem.

flickjo96

ok, i gave the wrong code info, i originally said the codes were po131 and po134 but i made a mistake. the real codes are po171 and po174 which are the lean codes. i replaced the fuel filter last night and cleared the codes and the CEL stayed off for a little over 50 miles and the truck ran a hell of a lot better but now the light is back on with the same codes and it annoys the hell out of me. i would really appreciate any suggestions or hints i could get.

flickjo96

no one has any input on what the problem is?

j-wilcox

Fuel pressure regulator.

Check it by removing the vaccum line from the regulator and wipe it dry.

Turn on the ignition but dont crank it over. Check the regulator for wetness. If its wet then its bad.

wde3477

^ +1 - thinking along the same lines, was going to suggest to check the fuel rail pressure to ensure adequate supply to the injectors.

If your model year has the MAF sensor - may try cleaning it. Other members have warned to be sure to use the proper cleaner for it. May also check for vacuum leaks, but I would think this would cause an increase in idle speeds first???

Basically, as I look at it - a lean code means the computer thinks it's getting too little fuel or too much air. This could be due to either an actual problem, or a sensor feedback problem. By a code being set, this means the computer has adjusted to its allowed limits with the perceived fault still present.

flickjo96

can anyone tell me where the fuel pressure regulator is located?

wde3477

Typically attached on the end of the fuel rail, opposite the fuel inlet end. Mine is back towards the rear of the motor. There will be a return hose. This regulator is about the diameter of a half-dollar, and will have a vacuum line coming off it.

j-wilcox

I dont have a location pic but this is what it looks like.