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2013 ATS Premium 3.6, 1989 Allanté
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Discussion Starter #1
Hi guys, have a 96 ETC with a few codes. tomorrow is my first bit of free time in a while so i figured Id tackle these codes and issues.

1) PC0122 - Throttle Position (TP) Sensor Circuit Low Voltage - History
2) PC0171 - Fuel Trim System Lean Bank 1 - History
3) PC0174 - Fuel Trim System Lean Bank 2 - History
4) PC0420 - Catalyst System Low Efficiency - Current
5) PC0503 - Vehicle Speed Sensor (VSS) Circuit Intermittent - History
6) IP2711 - PASSKey Open/Shorted Pellet After Good Key - Current

1) no idea what this is, but its history and id never seen it before so if it comes back ill check it then.

2,3,4) 2 and 3 were history but id had seen them before. i ran the codes more than 50 ignition cycles ago and these were there. so they must be just intermittent. i believe they may have something to do with 4. when i did a search for 4, everyone recommends replacing the cat converter but the reasoning is that the pre cat 02 sensor and the post cat 02 sensor arent reading like they should be. any chance the 02 sensor itself could be the culprit. does the 02 sensor have any effect on lean or rich conditions?
also, on some days, while i drive my eyes will sting. i know this has something to do with exhaust but given the codes i am getting, would a bad cat, O2 sensor, or a leak be to blame. if a leak was to blame, would that be the cause of codes 2 and 3?

5) this started showing up recently, along with a message "speed sensor fault". at first i thought it was from the transmission work that had been done last summer. the mechanic said that the input speed sensors had been popping immediately and he had finally isolated the problem. well the input speed sensor is inside the tranny and is an expensive fix. this code specifically says VSS which i understand to be mounted ON the tranny and is supposed to be a <$25 part. the symptoms i have are a wacky speedometer (of course) and transmission that wont shift properly or will "slip". in other words, while its driving its very firm, very well engaged throughout the whole shift points etc. every once in a while though it will forget to shift up and will just "slip" and rev past the shift point. i feel as though i need to take care of this one ASAP. im afraid its messing up my tranny. where can i find this VSS and is it something i can replace myself with a general toolset and a day off?

6) i get a message, something along the lines of "check theft system, vehicle may not restart" but it restarts, EVERY SINGLE TIME. i have not had an instance where the vehicle will not start (knock on wood). what could this be?

thanks in advance
 

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94 Eldorado, and a 99 ETC
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2,3,4) 2 and 3 were history but id had seen them before. i ran the codes more than 50 ignition cycles ago and these were there. so they must be just intermittent. i believe they may have something to do with 4. when i did a search for 4, everyone recommends replacing the cat converter but the reasoning is that the pre cat 02 sensor and the post cat 02 sensor arent reading like they should be. any chance the 02 sensor itself could be the culprit. does the 02 sensor have any effect on lean or rich conditions?
also, on some days, while i drive my eyes will sting. i know this has something to do with exhaust but given the codes i am getting, would a bad cat, O2 sensor, or a leak be to blame. if a leak was to blame, would that be the cause of codes 2 and 3?
The code just means that the pre-cat and post-cat oxygen sensors are both seeing about the same amount of oxygen in the exhaust. The cat converters job is to burn the remaining fuel and O2 from the exhaust after combustion. So the post cat O2 sensor shouldn't see as much O2 as the pre-cat O2 sensor. I think you may have it backwards though. I think the lean mixture is causing the computer to think that the catalyst system isn't working efficiently. After all, the cat converter can't burn off any oxygen if there's no fuel to combine it with. You may want to start checking your fuel system to make sure it's up to par. Check the fuel pressure, the FPR and all that fun stuff.

For your other stuff, I don't really know. Maybe someone else will chime in for that.
 

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White Diamond '03 DHS (with DTS floor shift)
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87,115 Posts
The lean condition is usually a vacuum leak. Start with that. See if you can locate and seal it. Then clear the codes and see what returns.
 

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2013 ATS Premium 3.6, 1989 Allanté
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Discussion Starter #5
Thanks guys.

Anything on the VSS. That's what's bugging me most right now. Its the most pronounced problem
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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VSS = Vehicle Speed Sensor. It is mounted on the right output shaft housing. Jack it up and pull the RF wheel and you can see it.
 

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2013 ATS Premium 3.6, 1989 Allanté
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Discussion Starter #7
thanks ranger. once i get that done ill attack the vaacum leak.

whats the worst place it could be (expense or difficulty in finding or removing and replacing the part). with my luck thats where it is
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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Hard to say, but I can't think of any place or thing that is a major problem.
 

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94 Eldorado, and a 99 ETC
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The lean condition is usually a vacuum leak. Start with that. See if you can locate and seal it. Then clear the codes and see what returns.
Good point! I didn't think about that... Could be the EGR valve is stuck open a little causing a vacuum leak and lean mixture.
 

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Super Moderator
White Diamond '03 DHS (with DTS floor shift)
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87,115 Posts
No, a stuck open EGR will cause it to stall at idle. Might not even start and would set a telltale DTC.
 
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