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Discussion Starter #1
Ok, did some searching and no one thread seemed to have all of the symptoms that my parents STS is having...

The thing starts worse than a diesel on a fridged winter morning no matter whether it was just running or it is cold.

They have TONS of codes for the O2 sensors. Replaced the upstreams (B1S1 & B2S1) because of heater codes (wish I didn't just delete that file that had the specific codes in it... grrr). All scans (with AutoTap) show perfectly working O2 sensors, but we still have persistant O2 sensor heater malfunction codes.

Also, at the same time that these codes pop up, they get a service stability system code and a traction control code.

All of this happens at the same time that there is a racket of clicking coming from both the dash and the trunk (relays me thinks). So, thinking there was a problem with a power wire (ground or positive) we tore basically the whole engine bay apart. Checked every and all grounds that we could find, pulled them off, cleaned everything up and put them all back together. Found like 5 or 6 all told. Then we put additional grounds from the battery to the core support, to the engine and then back to the firewall. We did find a positive lug that was corroded and thought that we had the problem solved.

For 2 days (80 some odd miles and about 6 full heat cycles), symptom free and mileage was up from a measily 15mpg avg to 25mpg avg (reset by the battery being disconnected). The car started great, as in you only had to barely move the key into the start region and the engine would fire to life.

Clicking started again, all the codes came back and it doesn't want to start nice anymore...

What are your thoughts. I'm basically thinking that something is wrong with the PCM or the ignition switch is on its way out. My experiences with ignition switches is that they either work or don't. I haven't seen one sorta work...

Let me know. They need help. They won't come close to passing the NY inspection coming up in a few months and they can't afford to spend the money for a waiver again this year.
 

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Discussion Starter #2
Ok so codes all came back and here's what they are:
PCM:
P0135 - Heated Oxygen Sensor (HO2S) Heater Performance B1S1
P0139 - Heated Oxygen Sensor (HO2S) Slow Response B1S2
P0141 - Heated Oxygen Sensor (HO2S) Heater Performance B1S2
P0147 - Heated Oxygen Sensor (HO2S) Heater Performance B1S3
P0155 - Heated Oxygen Sensor (HO2S) Heater Performance B2S1
P1139 - Heated Oxygen Sensor (HO2S) Insuff. Switching B1S2

TCS:
C1125 - Left Front Excessive Wheel Speed Variation
C1232 - Left Front Wheel Speed Circuit Open or Shorted

MSM:
B2120 - Lumbar Up/Down Sensor Failed


We switched B1S2 & B1S3, reset everything, and the EXACT same codes came back. Including both the Slow Response and the Insuff. Switching for B1S2... Something just doesn't seem right here. The codes didn't follow the sensor at all... I'm thinking that something still has to be wrong with the grounds.

It does look like they have a bad wheel speed sensor on the left front and they've known about the failed lumbar sensor for quite some time now. Its these O2 sensor codes that have been driving us NUTS!!!
 

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94 Eldorado, and a 99 ETC
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Check your fuses first before you do anything else, because I believe the O2 sensors are connected to one. It would be a fuse in the engine compartment.... other than that, it could very well be the PCM...
 

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Discussion Starter #4
Yeah, I guess I left out the obvious... Fuses were the first things checked. Both were perfectly fine.

I am leaning more and more towards a faulty ground. About the only one we haven't been able to check yet is the one on the back side of the engine block. That will be the next order of business, probably tomorrow if I can get out to their place.
 

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Discussion Starter #5
Ok, I just got in from doing some more wire testing. So here's what I have found. There is NO ground continuity at the O2 sensor connectors (black wire - pin C) unless the key is on - VERY ODD. With the key on, both pins C&D (black & pink respectively) have continuity to ground. Funny thing is that they both have 12v at them to ground as well... If these were shorted, shouldn't they have blown the fuses? Also, does anyone know of a relay that controls the current to the O2 sensors and/or one that controls the application of Ground???

This is very frustrating and I feel that even the wheel speed sensor codes are being caused by this overlying problem. Last year (at inspection time) they had B1S1, B2S1, and B1S2 replaced along with the LF wheel hub/sensor combo. Less than a month later, ALL codes returned exact same as before the repair work was done, but since they had already gotten a waver from the state on the inspection, they didn't pursue it until now when they are up for inspection again the end of next month.

Any help would be GREATLY appreciated.
 
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