Service Engine Soon Light

[02 Blue Thunder]

Looking for suggestions on my service engine soon light. I have a 97 Silverado Ext. Cab 5.7. The SES light comes on itermittenly, stays on for a couple of days and then goes away. But it always seems to come back on. I read in manual that the ses light deals with emissions system. I have replace everything in the emission sys and still does not work. Put it on a Genisis scanner and no hard codes were stored but did find a weak 02 sensor. Replaced it and still comes on and after a few days goes off. Anyone have any suggestions on what to check? It just seems strange that when using scanner with light on no codes show up. Hopefully not the ecm going bad. Thanks for any input.

 

Kyle

[GMCTech]

You'll have to get codes read with a good scan tool.

 

If the light has been on there is a code there, it just may not be readable with your scan tool.

 

Hope this helps.

[redvett]

Your truck has 4 02 sensors i you just changed 1 you got the wrong one you better get someone with a good scanner to check whats going on.

[02 Blue Thunder]

Mon, I will have it checked with another scanner, but the reason I only replace one of the 4, was because it was the only one registering bad. With the scanner, we checked the data streams in the ecm. The one on bank 1 pos 3 was not reading correctly but the others were, so I only replaced it. When I had a 97 before, I heard sometimes true dual exhaust would cause this problem. I had it done and never had a problem. Could that be the reason light is on now? Truck runs perfectly, so I am confident it is nothing serious.

 

Kyle

[Cool Zr2]

The one on bank 1 pos 3 was not reading correctly but the others were, so I only replaced it.

Then you replaced a sensor that isn't there, becasue there is no bank 1 sensor 3.

 

What engine do you have?

[02 Blue Thunder]

It was the downstream sensor on the drivers side exhaust. And it was there cause it cost me 69.99 at Autozone. 2 Downstream, 2 upstream. Not my first rodeo, just can't seem to find the gremlin in my emission system.

[Cool Zr2]

If something goes wrong with your truck the light somes on, not just someting related to the emissions.

 

Maybe you should drop it off at a dealer and let them go through it, maybe your flash (PCM programming) has a bug and needs to be redone, but if you do this make sure your Hypertech stuff is taken out.

[stebob]

My truck does this very same thing. The codes I always get are 172 and 175. Rich bank 1 and rich bank 2. Comes on and goes off intermittantly. I do have true duals. 2 in 2 out muffler. 5.7 Vortec. These are the only codes that are ever present. Over and over again. The truck seems to run great, however. After talking to a few others that have had the same issue as me, codes and all, discovered it was the fuel pressure regulator. I haven't changed mine yet, but my truck still does this..

 

Also,

I've replaced cap, rotor, wires, plugs, air filter, fuel filter and all the O2's and the prob. has never went away.

[02 Blue Thunder]

Thanks for the good replies. I will do some checking and have a different scanner used to see what code I can come up with. If need be I may have to have pcm flashed. Thanks for the input it is much appreciated.

 

Kyle