CEL Light ON after FPR replaced - Why?

I replaced my Fuel Pressure Regulator on my 02 Venture the other day and the Check Engine Light came on right after that. Error code "P0135 - Oxygen Sensor Heater Circuit Malfunction (Bank1 Sensor1)".

The vaccum hose was too loose on the new FPR so I replaced it with a new hose. I had the CEL reset by Advance auto parts and now it came back on. I don't understand why I'd get an error code right after replacing the FPR.

Has anyone seen this? Can anyone help me figure it out. I've looked at the prices for the 02 sensor but I really want to know if this sensor would go bad right after replacing the FPR before spending ~$70. for a new sensor.

My search on this site shows it might be a vacuum leak which I don't think I have after replacing the hose. What else should I check?

Thanks
Darren.

replaceing the FPR will not make the heater go bad in the o2 sensor. a vacuum leak would cause a lean code, not a heater circuit code. it could just be bad luck coincidence. other possibility is you knicked/chafed a wire at some point. that would normally cause a couple more problems, but is possible. in any case, would suggest replacing the o2 sensor.

Why did you replace the FPR to begin with?....to my knowledge; that's not a high problem part with the 3.4 motor....

I've replaced quite a few due to leaking, causing hard hot starts and so on. but is a good questions as to why it was replaced to begin with.

I had to replace the FPR because the original was leaking.

After installing the new FPR, I realize that the vacuum hose that attaches to the top of it was loose. I wasn't able to fix that until after the van was driven for a couple of days. When I finished the R and R, the CEL didn't come on when I test drove the van. My wife said it came on after she drove it for a little bit.

I replaced the vacuum hose with a new attachment piece from the local parts store. I did break the hose that's attached to the PCV but that was fixed at the time of the FPR replacement.

I was wondering if it's a vacuum leak that set the error code.

Well, I'm going to replace the upper 02 sensor.....now if only I can decide which one to buy since there are a number of choices.

Should I go for the cheapest one? ~ $40.00
Should I go for a direct replacement that's cheap? ~$60.00
Should I go for the only one that Advance Auto lists? ~ $74.00

The cheapest one does not come with a connector so I'd have to cut out the connector from the original one and reuse it on the new one.

Will keep the list posted on my progress.

P.S. It may not be a high problem part on the 3.4 but the fact that it's readily available at so many parts store and online at different price ranges suggest to me that it's a problem part. That and also the fact that it's also used on different GM vehicles.

Thanks for the responses/concerns.
Darren.

Well, if it were me, I'd get a Delco part....then you know it's right.

However, I'm concerned you'll be wasting your money....I think the problem probably goes back to the FPR remove & replace.

You mentioned the hose was loose on the new FPR and you repaired it - are you certain you didn't unseat the other end from the MAP sensor?

Also, did you check the fuel pressure with a gage and compare to specs after the FPR R&R? I'm concerned that the fact the hose didn't fit the new FPR properly may mean it's not the right one for the Venture; and now the fuel pressure is being regulated out-of-specs....I'll assume the new FPR isn't Delco....

Obviously it's difficult to nail down the cause over the internet. But I can say if I had a dollar for every O2 sensor that's been unnecessarily replaced I'd be a rich man right now.....besides, those things are a real pain to remove after 100K....they tend to almost get welded to the bung!

I'd look long and hard at that FPR R&R before jumping to the O2 sensor....

agree on the delco part, as one of the mods has in his signiture, OEM parts only hurt once! at any rate, replacing the FPR will not make the heater in an o2 sensor go bad. the sensor itself is still working fine or you would have other codes along the lines of P0130 to P0134, up to and including P0171 or P0172 for rich or lean codes. I did a lower intake gasket on a venture one time only to have the MIL light up on me. it was the heater on the o2 sensor that finally died at 135,000 miles. maybe a smidge of coolant got on it and fried it, or maybe it's time had come and went poof. I can also agree if i had 1 dollar for every o2 sensor replaced that wasn't needed, I'd be driving a ferrari now instead of an S-10. i see people posting that...and i quote..."I hit 60K on my vehicle, time to do a tune up and replace those o2 sensors". If it aint broke, don't fix it! lol. unless you have other codes in there besides the P0135, i would say the heater in the o2 is bad. all that does is heat the sensor up so it can start giving the PCM readings sooner, thus reducing emmissions and helping fuel economy a small bit.

I haven't checked the fuel pressure since I don't have the gauge to.

If I hadn't thrown out the original FPR, I would've put it back on to verify but that's too late.

What I'm going to do is double/tripple check very carefully that the vacuum hoses are not leaking and go ahead and replace the 02 sensor. Just because the error code is "Oxygen Sensor Heater Circuit Malfunction".

If the CEL light is still on, then I'll go back to the FPR.....either replacing with a delco part or first verifying if the pressure is indeed not correct.

The new FPR was purchased from autopart.com part # PR234. Although not delco I noticed it's listed at quite a few places for sale. I still want to trust that the part is not defective.

Darren.

unless it is leaking like the old one, or you are having fuel problems, i.e. hard hot restarts and so on, i would say the new FPR is ok. the light may not go out right away, so you may want to have the code cleared. if there is still a fault, then the code will come back pretty quickly.

darnsuprat, I have followed this and wondered what the outcome was. I replaced the air and fuel filter on my friends 02 Venture at 79k then saw that code.

Looking back at my friends records the air filter had 60k+ miles on it and fully caked as for the fuel filter, it was original. It did not have quite the pick up it has now after changing those two items. A bottle of fuel injector cleaner was added to a full tank.

The connection with your issue is, a half tank of fuel, after I did the above, the CEL came on with a P0135. I figured drive out the tank and get the code cleared and fill it up.

Within 30mi the CEL is back showing P0135. I will go through all the easy stuff before I change a sensor.

buckeye64,

I have planned to replace the 02 sensor but haven't done so as yet. I've checked over and over the work I did and everything seems ok. Vacuum hoses ok, FPR not leaking, van runs well etc. So, I'll try the 02 sensor next.......if they were so dang expensive, i'd have replaced it already. Besides expensive, there are so many to choose from and the oem one is expensive iirc.

I replace my air filter about every 20k miles which reminds me, I'm due for a change on mine about now.

buckeye64,

I have planned to replace the 02 sensor but haven't done so as yet. I've checked over and over the work I did and everything seems ok. Vacuum hoses ok, FPR not leaking, van runs well etc. So, I'll try the 02 sensor next.......if they were so dang expensive, i'd have replaced it already. Besides expensive, there are so many to choose from and the oem one is expensive iirc.

I replace my air filter about every 20k miles which reminds me, I'm due for a change on mine about now.

Any update on this yet darnsuprat? The 02 I have been working on where I saw the P0135, once I cleared the code It has not come back on after 2 tanks of fuel.

buckeye64,

I have not replaced the 02 Sensor as yet. I still can't afford to spend around $70.00 just so the CEL doesn't come on. I've been checking the code regularly to make sure no other codes are stored. It's still the P0135 code that is there.

Did you replace your 02 Sensor?

If it wasn't such a hard part to get to, I'd probably pick one up from the wreckers.

Thanks
Darren.

I am still waiting for the MIL to trigger. Now after several weeks nothing. I found no shorts/fuses/ground issues, so I wait.

the vacumn leak probably set the code off or it could have been lean burning as the fdr was leaking. get the codes reset then see if it comes back. the easiest way i have found to replace the bank one o2 sensor is to get on a set of ramps or rack and go up beside the exhaust pipe . you might spray some carb cleaner on the tip of the o2 sensor and clean it if it has a lot of crude on the tip.let it dry before you put it back in. i have cleaned some and put them back in and run them 100,000 miles with it working.also make sure the vacumn line is hooked up on the other end.the pvc line goes on the back valve cover make sure it is in the gromlet in the valve cover.also there is a gromlet under the throttle body plate that is attached to the pvc hose make sure the gromlet is still good shape as these are a softer rubber and will leak.