Same old truck, new problem

Huntaholic · July 22, 2003

Talk about a NIGHTMARE! I took my 98 Z71 in to have the clutch master cylinder and slave cylinder replaced last week. When I picked it up and drove it home, it was fine. I tried to start it a couple days later and the battery had mysteriously gone bad at only 5 months old. We got that all starightened out just in time for the SES light to come on. DTC code description says: bank1 sensor1 O2 sensor inactive. The mech. is just positive it is a bad o2 sensor, but I think a bad o2 would say something different such as: B1 S1 lean or something like that. He says no, its the sensor, I ask if he is willing to gamble the $92 the sensor costs and he agrees. He ccrawls under it, swaps the sensor while I clear the codes and Im off. AS SOON AS I PULL IN THE DRIVE AT HOME, SES AGAIN!

Does anybody have any idea what changing the clutch slave cylinder and master cylinder would have to do with the o2 sensor? We have already checked all the connections, swapped the sensor, etc...

If it was a broken wire, it seems that it would come on instantly but it takes around 15 miles of driving for the code to set, so I am lost!

Any ideas?

silverado man · July 22, 2003

If I remember right isn't there like 4 O2 sensors though. He might not have replaced the bad one.

Huntaholic · July 22, 2003

There are four, bank one is drivers side, sensor 1 is first from engine ( in front of cat) sensor 2 is after cat. I THINK!

AZ-Z71 · July 23, 2003

On my 99, sensor 2 is the the one after the cat. My SES light came on the other day. I had Autozone scan it and it told them it was bank 2 (maybe 1) sensor 2, which read low flow readings. The truck runs fine so Autozone said it was probably just the sensor and not the cat. Since I was going out of town and did not have time to mess with it I left it alone. They told me it was the one behind the cat. Price of the sensor is about $62 versus the dealer at $115. (dealer bastards)

Drove about six hundred miles and then all of a sudden the light went off. Drove another 50 to 100 and the light came back on. Probably change the sensor next week after payday!

stebob · July 23, 2003

I'm having a somewhat similar problem. My ses light comes on, too. Funny is that it'll come on for awhile then go off. May stay off for a week or 2 and come back on for a few days or stay on for a few days and go off for a few days. Drives me crazy. Scanned it and it shows rich bank 1 and rich bank 2(codes 172 and 175). Those are the only codes involved. I've tuned it up, replaced fuel filter, check fuel pressure, new air filter, new o2 sensors and the d**n thing still comes on. Truck seems to run good, but I have a feeling I'm losing a little power and dumping too much gas. I have no idea what to do now other than take it into the dealer and let the diag it. I'm scared it's a fuel injector. Anyone replaced one of these? Pretty difficult?

btw - I have a '97 Z71 5.7. ;)

AZ-Z71 · July 23, 2003

Fuel injectors are a breeze to do. Remove a few screws to get to the rails. Unplug the injectors and they pop out. If you are going to do this save yourself some money and buy them online. I think the online cost is like $45 a piece versus the dealer at $110 each. I had one go bad and had to buy it at the dealer. The truck was really running bad with extreme rough idle so I couldn't wait a few days.

stebob · July 24, 2003

It looks like the fuel injectors on the 350 Vortec are underneath the plastic intake manifold. I don't see any nor the fuel rails running outside. The 5.3's must be different than this. It looks like I'll have to pull the manifold and everything to get to them.

Huntaholic · July 24, 2003

stebob, I dont think our vortecs have actual injectors, but instead use a electronically controlled throttle body.

My diagnosis: Ok it seems that the mech. that did the tranny repair pinched the wire loom and the O2 sensor wire in between the engine block and the tranny when he put it all back together. As of right now, all is well again.