Had codes pulled today...help?
Thread Starter
Safety Car
Joined: Dec 2006
Posts: 4,290
Likes: 6
From: St Marys GA
Had codes pulled today...help?
Just had the PCM codes pulled from my '96 (no EMC or ABS codes, I checked those myself), and here are the problems:
-High idle
-Bank 2 o2 sensor running lean ::: FIXED, I think
-Not a code, but the reverse lights don't work ::: FIXED
So, what all should I do? The previous owner said he cleaned the IAC valve, and it worked for a couple of weeks before the light came on again, so that's not the culprit (at least cleanliness isnt....). I was thinking I should clean the TPS and maybe take a look at the TB to make sure it isnt gunked up, then cleaning the IAC valve again. If that doesn't work, I may have to replace the IAC valve? I'm not really sure.
The o2 sensor: The car has EM headers, random-tech cats and Corsa exhaust; I've heard stories of high-flow systems causing o2 sensor malfunctions due to them not reaching operating temperature. Do you think this is the case, and I should get o2 simulators? Or is it simply a bad o2 sensor...
Lastly, the reverse lights don't work. I checked the fuse, it's OK. I was planning on replacing the bulbs before I replace the reverse switch ($74, ugh), but is there anything else I should check?
Thanks!
-High idle
-Bank 2 o2 sensor running lean ::: FIXED, I think
-Not a code, but the reverse lights don't work ::: FIXED
So, what all should I do? The previous owner said he cleaned the IAC valve, and it worked for a couple of weeks before the light came on again, so that's not the culprit (at least cleanliness isnt....). I was thinking I should clean the TPS and maybe take a look at the TB to make sure it isnt gunked up, then cleaning the IAC valve again. If that doesn't work, I may have to replace the IAC valve? I'm not really sure.
The o2 sensor: The car has EM headers, random-tech cats and Corsa exhaust; I've heard stories of high-flow systems causing o2 sensor malfunctions due to them not reaching operating temperature. Do you think this is the case, and I should get o2 simulators? Or is it simply a bad o2 sensor...
Lastly, the reverse lights don't work. I checked the fuse, it's OK. I was planning on replacing the bulbs before I replace the reverse switch ($74, ugh), but is there anything else I should check?
Thanks!
Last edited by StealthLT4; Dec 20, 2007 at 11:30 PM.
Race Director
Joined: Sep 2000
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From: The Top of Utah
For the code(s) the best course of action is to follow the trouble shooting charts in your FSM for whatever codes are displayed. The TPS is external to the TB and not likely to need cleaning, but it can't hurt to look it over. It is possible for the IAC to get gunked up, again, quickley depending on conditions. If the IAC is gunked up, or if it wasn't done at the last IAC cleaning, the IAC passages in the TB should definitely be cleaned. If you are having problems staying in closed loop then heated O2s are likely the cure.
The high idle isn't likely caused by whatever set the code for the O2. Along with the IAC maintenance, check very closely for vacuum leaks.
For the back up lamps, the trouble shooting is pretty basic. Is there power to them when there should be? Are the bulbs burned out? Don't replace the back up light switch with out first testing it.
RACE ON!!!
The high idle isn't likely caused by whatever set the code for the O2. Along with the IAC maintenance, check very closely for vacuum leaks.
For the back up lamps, the trouble shooting is pretty basic. Is there power to them when there should be? Are the bulbs burned out? Don't replace the back up light switch with out first testing it.
RACE ON!!!
Thread Starter
Safety Car
Joined: Dec 2006
Posts: 4,290
Likes: 6
From: St Marys GA
Thanks! I have the FSM, but I couldn't find much of any help as far as diagnosing problems. It sure will help figuring out how to take some of this stuff off though.
The Vette's getting a state inspection right now, but I'm gonna start testing stuff as soon as I get it back. I'm sure I'll post again if I run into any problems.
The Vette's getting a state inspection right now, but I'm gonna start testing stuff as soon as I get it back. I'm sure I'll post again if I run into any problems.
Drifting
Joined: Aug 2006
Posts: 1,326
Likes: 18
From: Los Angeles California
Seriously? Practically the whole FSM is big flow charts of diagnostic procedures... There are ones for the codes your car threw, there is one for the backup lights, there is one for almost everything. Even if you have that goddawful half-complete "preliminary" manual.
Instructor
Joined: Nov 2007
Posts: 108
Likes: 0
From: Waukesha WI
First, and this is just a thought as i may be way off base, but the o2 sensor may be causing the high idle. Second, you say the state has your car for an inspection. I keep seeing that here, why is that? I've never heard of the state of Wisconsin taking a car for inspection unless they were inspecting it to give it a new title from a salvage title.
Thread Starter
Safety Car
Joined: Dec 2006
Posts: 4,290
Likes: 6
From: St Marys GA
In VA we have to have it inspected yearly. It's just a safety thing. Make sure all the lights work, no holes in the exhaust, no holes in the floor...stuff like that. I just got it back; I'm actually surprised it passed with no reverse lights, but I'm not complaining..
Drifting
Joined: Aug 2006
Posts: 1,326
Likes: 18
From: Los Angeles California
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Thread Starter
Safety Car
Joined: Dec 2006
Posts: 4,290
Likes: 6
From: St Marys GA
OK, did some more work on it. Cleaned the o2 sensor (REALLY dirty, black gunk), as well as the IAC valve and the TB (what I could clean without taking it off). Disconnected the battery for 30 min to reset the PCM.
Result: Initially, it idled well and the exhaust smelled right (not rich). Let it sit for a few minutes idling perfectly, then drove it around to get up to operating temperature. Almost immediately, the idle went back to the ~1100rpm idle it has been at. After about 15 minutes, the Service Soon light came back on. I haven't scanned it yet, but I'm betting it will be the high-idle code. Any more ideas on this high idle situation?
Result: Initially, it idled well and the exhaust smelled right (not rich). Let it sit for a few minutes idling perfectly, then drove it around to get up to operating temperature. Almost immediately, the idle went back to the ~1100rpm idle it has been at. After about 15 minutes, the Service Soon light came back on. I haven't scanned it yet, but I'm betting it will be the high-idle code. Any more ideas on this high idle situation?
Drifting
Joined: Aug 2006
Posts: 1,326
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From: Los Angeles California
Le Mans Master
Joined: Feb 2006
Posts: 8,753
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From: Louisiana
First. You will want to fix the O2 sensor code. The 96 stock O2 sensors should be heated (3 or 4 wire). To follow the FSM and fix the code you will need a real time scanner. If you don't have a scanner, which I assume you don't if someone pulled the codes for you, then you might get lucky by replacing the O2 sensor in question (not cheap though). No amount of cleaning will work with O2 sensors. They are delicate to any type of solvents, ect. Also check the wiring and connection to the O2 sensor and make sure the wires have not grounded on the exhaust or cat if you have them. After the code is gone, see if the high idle is still there. You will want to make the stored code disapear before starting on the idle situation. O2 sims will most likely benefit you on the post cat sensors.
For the backup lights, just follow CFI's advise. Make sure your getting voltage to them when the tranny is in reverse. Place blocks behind the wheels and pull the e-brake if you don't have help. If you get voltage at the light plug, replace the bulbs.
For the backup lights, just follow CFI's advise. Make sure your getting voltage to them when the tranny is in reverse. Place blocks behind the wheels and pull the e-brake if you don't have help. If you get voltage at the light plug, replace the bulbs.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by LouisvilleLT4
Statewide inspections for road safety as opposed to emissions? Now that is something I can get behind
Originally Posted by LouisvilleLT4
Seriously? Practically the whole FSM is big flow charts of diagnostic procedures... There are ones for the codes your car threw, there is one for the backup lights, there is one for almost everything. Even if you have that goddawful half-complete "preliminary" manual.
It's all in there.
RACE ON!!!
Drifting
Joined: Aug 2006
Posts: 1,326
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From: Los Angeles California
Or just turn the ignition to "on" without starting the engine and put the transmission in reverse.
Thread Starter
Safety Car
Joined: Dec 2006
Posts: 4,290
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From: St Marys GA
I'm working my way through the FSM...some of that stuff is kind of over my head though. I'm doing what I can.
Just bought a multimeter tonight, so will begin working on the reverse lights now.
It's a manual, so yeah, I'm not gonna start the car and chock the wheels in reverse
Just bought a multimeter tonight, so will begin working on the reverse lights now.
It's a manual, so yeah, I'm not gonna start the car and chock the wheels in reverse
Drifting
Joined: Aug 2006
Posts: 1,326
Likes: 18
From: Los Angeles California
I'm working my way through the FSM...some of that stuff is kind of over my head though. I'm doing what I can.
Just bought a multimeter tonight, so will begin working on the reverse lights now.
It's a manual, so yeah, I'm not gonna start the car and chock the wheels in reverse
Just bought a multimeter tonight, so will begin working on the reverse lights now.
It's a manual, so yeah, I'm not gonna start the car and chock the wheels in reverse
If you want to read the amperage that circuit is using, you can pull the fuse associated with it (diagrams of all fuse wiring are in the beginning of the electrical section), switch your multimeter to DC amperage using the "unfused" slot, and use the probes where the fuse goes. To measure voltage, remove the light and measure between the hot and ground wiring terminals (but don't try to measure amperage there, as explained above).
Last edited by LouisvilleLT4; Dec 14, 2007 at 08:38 AM.
Thread Starter
Safety Car
Joined: Dec 2006
Posts: 4,290
Likes: 6
From: St Marys GA
Thanks for the tips. I've been playing with multimeters this whole semester in my Electrical Engineering class, so I'm almost sick of using them... I splurged and got a nice Craftsman auto-scaling multimeter though, so its pretty painless.
I got the reverse lights working...apparently it was just a loose wire somewhere, because they worked when I put everything back together. Thank GOD I don't have to buy a new switch...
I cleaned the o2 sensor with TB-cleaner, and the code hasn't come back, but I read somewhere that they don't work properly when cleaned, and they have to be replaced. Is this true? I want to make sure this is fixed before I continue chasing the idle problem, as it could be contributing.
Also, I can't find the IAC valve on gmpartsdirect.com. It has to be on there, I just can't find it. Has anyone?
I got the reverse lights working...apparently it was just a loose wire somewhere, because they worked when I put everything back together. Thank GOD I don't have to buy a new switch...
I cleaned the o2 sensor with TB-cleaner, and the code hasn't come back, but I read somewhere that they don't work properly when cleaned, and they have to be replaced. Is this true? I want to make sure this is fixed before I continue chasing the idle problem, as it could be contributing.
Also, I can't find the IAC valve on gmpartsdirect.com. It has to be on there, I just can't find it. Has anyone?
Le Mans Master
Joined: Feb 2006
Posts: 8,753
Likes: 9
From: Louisiana
Unleaded fuel is essential to the proper and continued operation of the O2 sensor. Never use cleaning solvents of any kind on the O2 sensor, solvents can permanently contaminate the sensor element. If the sensor has over or around 50K miles on it..replace it as they get sluggish with age.
If your not looking to purchase just a GM IAC, Autozone or most any other auto parts stores carry them for around $35. As stated, resolve the code and go from there.
Race Director
Joined: Sep 2000
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From: The Top of Utah
Originally Posted by jwalker87
I'm working my way through the FSM...some of that stuff is kind of over my head though. I'm doing what I can.
Originally Posted by jwalker87
I cleaned the o2 sensor with TB-cleaner, and the code hasn't come back, but I read somewhere that they don't work properly when cleaned, and they have to be replaced. Is this true? I want to make sure this is fixed before I continue chasing the idle problem, as it could be contributing.
RACE ON!!!
Thread Starter
Safety Car
Joined: Dec 2006
Posts: 4,290
Likes: 6
From: St Marys GA
Well, doing a fuel injector balance test is out of my league, at least without sending them to a shop. That was I think the second item on the diagnostic list.
When I had the car scanned (I have a scanner now though
), one of the codes was for the bank 2 o2 sensor. When I took it out, it was pretty caked in sut. Also, you could tell the car was running rich just by the smell. Performance-wise, it still felt/feels good.
I'll get a new o2 sensor. Then see if that has any effect on the idle.
The thing about the ide is; if it were injectors, or a vacuum leak, it would also cause problems across the RPM band, correct? The only problem is that it idles at 1100rpm instead of ~800. There's a small amount of searching, but no more than 100rpm or so.
Also, before I come to a stop, it will idle around 1600-1900rpm (ex: pushing the clutch in to drift down a hill). And if I give it a little bit of gas while its idling at 1100, it will settle down to 900-1000 for a while before returning to 1100rpm.
When I had the car scanned (I have a scanner now though
), one of the codes was for the bank 2 o2 sensor. When I took it out, it was pretty caked in sut. Also, you could tell the car was running rich just by the smell. Performance-wise, it still felt/feels good.I'll get a new o2 sensor. Then see if that has any effect on the idle.
The thing about the ide is; if it were injectors, or a vacuum leak, it would also cause problems across the RPM band, correct? The only problem is that it idles at 1100rpm instead of ~800. There's a small amount of searching, but no more than 100rpm or so.
Also, before I come to a stop, it will idle around 1600-1900rpm (ex: pushing the clutch in to drift down a hill). And if I give it a little bit of gas while its idling at 1100, it will settle down to 900-1000 for a while before returning to 1100rpm.
Race Director
Joined: Sep 2000
Posts: 17,298
Likes: 33
From: The Top of Utah
A code only identifies the circuit a bad, out of parameter, reading came in on. If the mixture is out of kilter a code could be set because the O2 correctly read a mixture that shouldn't exist and that the O2 didn't cause. You need to trouble shoot each code, each time, to isolate and cure the CAUSE of the problem. Once the culprit is located, it needs to be tested to ensure it really is bad. Otherwise you can waste a lot of money replacing good parts. Like I keep preaching, don't shoot the messenger.
No. Not necessarily.
The idle problem isn't likely to be injectors. The O2 code very likely may be.
That may be caused by a vacuum leak or even a warn, sticking, TB. Step one is to fix the cause of the codes. Then, you should find additional trouble shooting charts in your FSM that addresses the drive-ability problems, like your high idle.
RACE ON!!!
Originally Posted by jwalker87
The thing about the ide is; if it were injectors, or a vacuum leak, it would also cause problems across the RPM band, correct?
Originally Posted by jwalker87
The only problem is that it idles at 1100rpm instead of ~800. There's a small amount of searching, but no more than 100rpm or so.
Originally Posted by jwalker87
Also, before I come to a stop, it will idle around 1600-1900rpm (ex: pushing the clutch in to drift down a hill). And if I give it a little bit of gas while its idling at 1100, it will settle down to 900-1000 for a while before returning to 1100rpm.
RACE ON!!!