I have a 2004 CTS. While backing out of the garage the engine felt like it was running on 2 cylinders then the engine light started flashing. I took it to a garage I always use and they ran diags and told me the main computer went out and they had to order one directly from GM. They also told me this caused other problems as well. The cost is outrageous. Am I getting taken?

I had something similar happen on my 2004 CTS. The car would not crank, and I recall the security light was on the dash. The key could be turned off, but not quite far enough to be removed.
The key can be removed by sticking a small pin or screw driver in a hole under the steering column... maybe 2 inches from the actual steering wheel. I recall there is a small cover or plug in the hole that needs to be removed.
You can let it sit and occasionally try to start it. My did start once more.
I ended up having it towed to the GM dealer and they replaced the ECM for about $500? That took care of it for a couple years, until I recently sold it.

Error code p0300 indicates rough idle and p0305 indicates engine misfire in cylinder 5. Check for faulty spark plug and its wiring. Also check for ignition coil and distributor. Replacing spark plug and its wiring may resolve the issue.

Rob, when the battery is disconnected for any reason a couple of things happen, and frankly it's a design error on the GMT360 platform (Envoy/Trailblazer). Your mechanic did not make an error here. Issue #2, your vent actuators blew out when the battery was re-connected back up, it happens, it's common. Issue # 1 is a little more complicated. The flashing light means misfire, is a seperate issue and a coincidence. Pull the codes out with a scanner and report back, may be bad coil pack, happens and is common. Idle problem and starting to die is an easy fix, betting it only happens when the AC or defrost is on. Disconnect fuse #10 and #28 under the hood. Remove the throttle body and clean it with a sensor safe spray like Seafoam. Drive it around for the computer to relearn the newly cleaned throttle body. Idle problem will be fixed.

2005 CTS 3.6 Dead battery, key stuck, service anti theft and nothing happens when you turn key, Ttried everything, ECM reset, key memory reset, charged battery to 12.7 volts, locked door w remote and opened w key, anyway you get the idea. After 3 days of online reading and trying, THIS IS WHAT WORKED, 1. put key into on position 2. removed sarter relay from front fuse panel 3. jumped 1st pin closest to fender and passenger seat with pin that is closest to motor and front fender. I used a paper clip and just made contact long enough for car to start. ran car for five minutes and took key out and everything went back to normal. then I took car to advance auto parts to have engine light reset. if car does not go back to normal you have ECM (car computer) failure. video on YouTube under "no crank, no start"

2004 Cadillac CTS 3.6L SFI DOHC 6cyl
Firing order 1-2-3-4-5-6 ------- front ' 1 3 5 ' of ' ' vehicle ' 2 4 6 ' ------- distributorless ignition


2004 Cadillac CTS 2.8L SFI DOHC 6cyl
Firing order 1-2-3-4-5-6 ------- front ' 1 3 5 ' of ' ' vehicle ' 2 4 6 ' ------- distributorless ignition


Hope this help (remember rated this free answer).

How do I reset my alarm in cts 2004

yes i would change the plug wires , you can take a spray bottal with water and spray that wire, and if it starts to run real bad then it is shorting out, you may also have a injector going bad you can test this buy puting a ohms meter on it and ck the ohms it should read the same or close to the same as the other if not it will need replaced

TRY REPLACING THE CRANKSHAFT POSITION SENSOR..HAVE SEEN THESE CAUSE MISFIRES AND LOW VOLTAGE DTCS AS PCM THINKS VEHICLE IS NOT RUNNING..ALTERNATOR MAY NOT BE PUTTING OUT PROPERLY

i also have a 2002 VW Polo 1.2, which I bought in January this year. The first time i drove it the engine management light came on. I took it to a garage and they changed a sensor in the exhaust system at a cost of £350. I drove the car again the following week and the light came on again, I took it to the same garage and they told me it was unrelated and that i needed another £300 repair. Refusing this I took the car to my parents mechanic who told me that these lights are prone to coming at the slightest little thing and to ignore it if the car is driving fine and sounds normal. He said that if there was a genuine problem that you wouldn't need the light to tell you but that the problem would be obvious through the sound it made or by the way the car started to drive. He said he felt the sensors were over sensitive and were there largely to encourage owners to take their cars into the garage for expensive repairs which didn't need doing.
He told me to drive the car as normal and ignore the light. He said only take it to a garage if there is an obvious problem, otherwise I was wasting my time and money.
I now drive the car without worrying abou the light and so far I haven't had any problems.
Suggest you do the same.

It sounds like u got a coil pack going out. Alot of times when your engine is cold or when you arn't putting a load on it the coils won't fail. How ever when the engine reaches operating temperatures and there is load on the coils that is when they are going to break down. my advice would be to get a scanner and see what cylinder the missfire is at then swwap that coil to another cylinder to verify that the coil is defective. If it is purchase another with a new spark plug put it in and let it rip.