22 replies to this topic

[Reverend Blair]

The check engine light in my truck came on. Checked the oil and the coolant and the transmission fluid and even the power steering fluid, since I have no idea what has sensors and what doesn't. Then I checked for leaks, obviously bad wires, slipping belts, etc.. All is well and good.

So I went on-line and started looking around.  Could be a loose gas cap (nope), an O2 sensor, a bad solenoid somewhere in the evaporation return system, or just about anything.  No idea where to start.

So I phone my BIL, who owns a similar truck and has some experience with these things. He says to phone his brother because he has a code reader and is an actual mechanic.

"Is the CEL flashing?" He asks.  
"No."
"Then you can drive it. Could be anything, but if it's not flashing you won't hurt anything.  Stop by sometime and pick up the code reader. It's easy to use."

So now I have to drive to the other end of the city this evening and pick up the code reader.  With all these computers and sensors, why can't they have a little display that says, "Dude, replace the following component(s)?" That would eliminate the need for a code reader and make me hate GM a little less. They may be my favourite pick-up maker, but only because I've had even worse luck with the other two.

[KennyP]

The only reason it doesn't tell you what to replace is because the GM mechanics would like to keep their jobs. They are making them hard enough to work on as it is so you'll take it in for the repairs.

[Reverend Blair]

The mechanics will always have jobs...just like they did when things were simple enough that all you needed was a case of beer and some wrenches to make small repairs on your own vehicle. The thing is that you could buy aftermarket parts, install them without special tools or diagnostic equipment, and the guys in suits never saw a penny of it.  If you couldn't handle the repair yourself, you could take it to a local place where the owner actually showed up and worked every day.  I've never minded giving money to a mechanic for the work they do, or a local business owner.  It's the guys in the suits who get the biggest cut now though, and they never get their hands dirty.

Ah well, having a BIL that's a mechanic helps me get around some of that.  I can borrow the code reader and if it's something too complex for me to do on my own (seems to happen a lot now) I can get him to do it.  I just hate bothering him with it because I know he has better things to do.

[massey driver]

I can tell you this its just as bad with off road vehicles and probably all the newer farm/constrution equip etc: etc: . thankfully with the internet there's lots of help for guys like me with some nohow and some tools [good amount of tools] to beable to still work on the newer stuff.But your right when I was younger and worked on vehicles most things were pretty straight forward back then.Still there was no shortage of work for mechanics[ technicians nowadays] to keep us busy. Lot of people have no clue how to put air in there tires,or check the oil,never mind do any kinda fixing.So I do agree that things can be simpler to fix repair and there still wouldn't be a shortage of vehicles needing repairs done by others.

[Billygoat]

My '01 dodge, you turn the key off/on-off/on-off/on, then any codes will come up on odometer. Look online to find what codes mean. Mine kept saying vacuum leak. Couldn't find anything wrong. Paid $75 to have smoke test done. Found switch that told computer the vacuum system was ok had gone bad. Vacuum system ok. Another problem- truck starts fine run fine for a few minutes, then runs like crap for a few minutes, runs fine until the next startup. NO codes, found front o2 sensor was bad. New sensor from o2sensors.com, runs like a champ. Diagnostics on this truck are terrible, along with MPG. Truck is great other than that.

[vbob]

A gm pick up with a check engine light is most commonly a vent valve problem, but I would also remove to gas cap and look at the seal, usually a gray plastic looking ring, if you can see a black ring build up, clean it and the top of the filler neck off with a rag wet down with brake cleaner, it will cause a leak turning on check engine light.

[Reverend Blair]

Went down to me BIL's and he plugged in his code reader.  Nothing. No codes.  Engine light was still on.  Drove home.  Halfway here the light went out.  Now I'll be wondering about forever. Or maybe not...truck runs fine, doesn't burn oil, radio works okay.  Sure, the speakers are a little rattley and they put the ashtray too far away from the driver's seat, but I've adjusted to that.

[Michiganmobileman]

Reverend Blair said:

Went down to me BIL's and he plugged in his code reader.  Nothing. No codes.  Engine light was still on.  Drove home.  Halfway here the light went out.  Now I'll be wondering about forever. Or maybe not...truck runs fine, doesn't burn oil, radio works okay.  Sure, the speakers are a little rattley and they put the ashtray too far away from the driver's seat, but I've adjusted to that.

That's funny to hear that makes me remember Kathy grumbling about that on a truck she had before seems like it was an 03 or 04?  Now have an 07 Chevy and its back within reach while driving.  Guess that was to help you quit smoking.

[ducky]

Guys always remember that an O2 sensor code or any other code does not mean that that component itself is TU.  It could be any of a number things.  Depending on the code it will tell you several thing to point you toward the problem like  "Ground"  (OORH - OORL) - "Signal" (OORH - OORL) - "Sensor supply" (OORH - OORL).  
Any Engine ECU/ECM will look for the above situations and warn you of a problem.  It monitors all sensor and actuator circuits for these issues.
"OORH" = (Out Of Range High) = A part of the circuit may be shorted to B+  or  Sensor Ground Open
"OORL" = (Out Of Range Low) = A part of the circuit may be shorted to B-  or  Sensor circuit shorted to Ground

Any of these situations will cause a sensor code and in My experience it is usually a poor connection or short in the wire harness.

A vehicle may operate OK warm but set an O2 sensor cold if the O2 heater circuit is open or in operative.  i.e. no B+ or no B-

Just some food for thought.

[Reverend Blair]

Michiganmobileman said:

That's funny to hear that makes me remember Kathy grumbling about that on a truck she had before seems like it was an 03 or 04?  Now have an 07 Chevy and its back within reach while driving.  Guess that was to help you quit smoking.

Mine is an 04, so that makes sense.

[Reverend Blair]

ducky said:

Guys always remember that an O2 sensor code or any other code does not mean that that component itself is TU.  It could be any of a number things.  Depending on the code it will tell you several thing to point you toward the problem like  "Ground"  (OORH - OORL) - "Signal" (OORH - OORL) - "Sensor supply" (OORH - OORL).  
Any Engine ECU/ECM will look for the above situations and warn you of a problem.  It monitors all sensor and actuator circuits for these issues.
"OORH" = (Out Of Range High) = A part of the circuit may be shorted to B+  or  Sensor Ground Open
"OORL" = (Out Of Range Low) = A part of the circuit may be shorted to B-  or  Sensor circuit shorted to Ground

Any of these situations will cause a sensor code and in My experience it is usually a poor connection or short in the wire harness.

A vehicle may operate OK warm but set an O2 sensor cold if the O2 heater circuit is open or in operative.  i.e. no B+ or no B-

Just some food for thought.

Yeah, but mine had no codes when we plugged the reader in.  What does that mean?

[caseguy]

Reverend Blair said:

Yeah, but mine had no codes when we plugged the reader in.  What does that mean?

It could mean that it was a transient or intermittent problem that has resolved itself for now. Don't be surprised if the light comes back on...or doesn't!

[ducky]

caseguy said:

It could mean that it was a transient or intermittent problem that has resolved itself for now. Don't be surprised if the light comes back on...or doesn't!

Ditto!

[Reverend Blair]

I'm wondering if it could have been caused by frost/moisture.  We had three days of thick fog with temps right around freezing, and my drive to work is about ten minutes.  The drive to my bro in-laws was the first chance the truck really had to warm up during that period.

[ducky]

That is possible Rev.  Drive it a few days and see what happens.  Wire harness connections can cause some very illusive intermittents.

If possible get some one that can go ind look at the code history.  That could steer you in the right direction.  Least a few thinks to check out.