Originally Posted by Gumby22

The new codes are set because the sensor element isn’t properly inserted into the exhaust stream and so it’s unable to function properly. O2 sensor spacers are intended for use on vehicles that have had the emissions controls deleted - they won’t solve any problems on stock systems.

On these engines, intake and exhaust leaks are the most common problems, followed closely by weak fuel supply and/or incorrect fuel (E15 or higher ethanol blends when the engine isn’t rated for it).

If you want to resolve these codes, you need to methodically analyze the related components for proper operation to determine the cause. If you’re unable to do so, take the van to a shop you can trust.

Speaking for myself, I can help guide you through the diagnosis, but only if you’re willing to follow the advice/directions given, and at this point, you have tests that can be done to bring you closer to the answer. If there’s anything about my instructions you don’t understand, by all means, ask for clarification.

Originally Posted by Idkchevy1234

question where can I find the fuel pressure regulator on this van ?

Originally Posted by mountainmanjoe

there is none.

Fuel pressure is regulated by the computer using the fuel pump and a pressure sensor.

Originally Posted by mountainmanjoe

again ...


there's a port on the fuel rail where you can stick your gauge if you want to test the pressure.

Originally Posted by mountainmanjoe

again ...


there's a port on the fuel rail where you can stick your gauge if you want to test the pressure.

Originally Posted by Gumby22

P0171/P0174 - Are there any leaks at the exhaust manifolds? If so, those need to be repaired before pursuing other possible causes of these codes. The leaks will allow excessive oxygen into the exhaust stream and skew the sensor readings.

Low fuel pressure is another possible cause. Spec is 50-60 PSI at the rail - should hold for at least a few minutes at KOEO and maintain it KOER at idle. The regulator is part of the fuel pump assembly in the tank.

P0121 - clean the throttle body bore, if necessary. Carbon accumulation around the throttle plate can cause it to stick/drag/bind and intermittent stalling and/or idle concerns can result.

If the TB is clean, monitor the TPS signal KOEO and slowly press the accelerator pedal all the way to the floor and slowly release. Watch for sudden changes in the signal that aren’t the result of your movements. Any sudden changes indicate the throttle body requires replacement.

Originally Posted by mountainmanjoe