I've wanted a Gen 1 CTSV since they first came out, however it had always been a goal/dream for me with my financial upbringing. However it was something I was passionate about, and would talk with my mom about. Well, I lost my mom in a tragic accident. I received a settlement from the accident, and used a large portion of the money to fulfill that dream I would talk to her about. I found a 2005 ctsv with a maggy already installed. So I drove down from the bay area to laguna hills area to purchase it and drive it back. Drove all the way back to the bay area, and she drove like a charm outside of a slight mishap when the drip/splash guard came off under the car due to it being so low and my dad driving over a piece of truck tire in the middle of the highway. I drove it around town for a little over a month, and not even getting on it as I was still getting use to A. Driving a force inducted car, and B. The throttle response. Then one day I get in it to pick my son up from school, and on the way home the car went into reduced power and the dash lit up saying multiple things like engine oil temp to high, engine oil low, traction control, abs, and cruise control. My heart dropped, however I was confident my fluids were good. As soon as I got home I checked the oil level and it was good, yet against my better judgment I added about 3/4 of a quart. Then the next day I go to take my son to school and my battery is dead, and had to have his mom pick him up and take him to school while I figured out what was going on with my car. I took my battery out to charge it, and when I installed the charged battery it was still going straight into reduced power with little to no throttle response. I ran the codes with the cheap harbor freight global obd2 scan tool, and it had the codes P1516 P0120 P0220. I pull up the codes on mitchell ondemand and do some online reshearch on the codes. After gathering some basic info on the codes I figured it was a dirty TB, and even tho it looked pretty clean I went ahead and cleaned it according to the service manual directions. However I was still getting the same codes, and still in reduced power. Long story short it's been almost 6 months with my car parked, and I've tried swapping the Throttle body, the APP, and the TAC, along with installing a new TPS, and redoing the pigtail from the baggy install. After banging my head into my computer monitor from confusion & frustration I figured maybe I got the two TPS signal wires switched. I guess I figured since the 120, and 220 codes were saying correlation issues with the signals, that I would try to switch them. So.... After switching them the codes go away and don't reappear, however I get a P2101 code instead and the TP% is at 88.2%, yet the car idles fine. I dont have the money to tow it to the dealer and pay whatever it is they try to get me for. I dont know what the hell is going on, but I need to fix it so I can get back to work. Please help me figure this out.

 

Didn't mean to post this in this section, maybe one of the forums moderators would be nice enough to move this to the appropriate section for me, I would really appreciate it. Sorry.

Oh, I've also cleaned most of the grounds, along with adding ground wires straight from neg terminal to the pcm housing, to the throttle body, and back to the negitive terminal. Cleaning the grounds did help a lot of little things I had noticed. Like the alarm, Windows, trunk, and even improved the data communications, cause the scanner started giving me more info.

 

P1516...if youve tried a different throttle body and no change you may need to replace ECM
P0120 and P0220 .... Same as above if youve tested circuits, changed out TB and no change , replace ECM
New ECM id bet

 

Just to better understand, and further my knowledge of my cars system and how it is controlled by each module. Can you elaborate as to what makes you think it would be my cars computer? My car is actually equipped with a PCM, however assuming you meant PCM I don't understand why the car has a throttle actuator control module if the pcm does all the controlling of the throttle. Seems pointless to run the data through an additional module if it's just going to be controlled by the PCM? Also, why wouldn't GM have a PCM replacement in the flow chart for any of the 3 codes? Are you suggesting the PCM is bad based on prior experiences, or just speculation based on what you've heard? I'm not saying I you're wrong, and will consider it if I could understand how and why it could be the PCM. Looking at the circuit I can't visualize how it could be, however I'm no expert at circuitry and how a cars PCM works completely. I do appreciate the suggestion, and hope you or someone else might be able to elaborate.

 

The PCM and the TAC work together. Given the difficulty of troubleshooting these engines and the fact that very few of us have access to dealership-level scan tools for problem solving, we keep spare, junk yard acquired PCM's around.

These spares need to be re-flashed with operating system changes to make them support our vehicles and I have two configured spare PCMs on the shelf here and I tinker with a third. I picked up the spares at my local junkyard for anywhere between $18.50 on sale days to $38 on regular days. This costs money for somebody with HP Tuners ($150 around here) to make the PCM software changes or you can use a combination of Tuner Pro RT and LS Droid. Doing this yourself can save you money but the risks and learning curve are steep and perilous. You can melt a piston if you run your engine too lean or turn your PCM into a wheel chock brick if you are not careful. You could also take a junk yard PCM to a dealership for a flash but this will also cost an unknown number of dollars.

Welcome to the world of being your own high tech 21st Century mechanic.

Rick

 

Before replacing the PCM, I’d recommend pulling and saving the current tune file in your car. Clearly it’s been tuned already for the Maggie, so save yourself some additional money redoing the tune on a new PCM. You’ll need someone with HP Tuners or EFI live or similar software to do this. PCM’s are relatively cheap, so worth a shot in this case. A new tune will be quite a bit though. Get that file before ditching the old one.

 

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