When a replacement ECM doesn't want to make nice with the keys

Have you ever heard the saying "Fool me once, shame on you. Fool me twice, shame on me?", or "Sometimes I'm my own worst enemy?" I'm sure we can all relate to having said both of those at one time or another.

I had reason recently to have to use each saying while working on a 2004 Cadillac CTS (DM). Actually, it was the second time working on the same car, with a similar problem each time, where I screwed up the most. I promise there will not be a third time, and I’ll share with you my experience, so that hopefully you won’t be using those sayings in the future.

As a preface, when an ECM is replaced on almost every GM vehicle built since 1990, the replacement module will have to be programmed. In most cases, after module programming, there will be a need to perform additional functions in order to make the new module work correctly in the vehicle in which it was installed. One of those functions may be VTD (Vehicle Theft Deterrent) Relearn, where a module or the ignition key(s) will be registered to work in this vehicle.

Over the years GM has developed several different types of VTD systems, but if we have the factory tools for the vehicles on which we work and if needed, a Locksmith’s Identification (LSID) certification, there should be nothing that would be a problem for us to do.

Patience is a virtue

It seems problems are more likely to occur if you are in a hurry. Taking time to research an anti-theft relearn on a GM would use up valuable time when it was already late on a Friday afternoon. Besides, I thought, this car is no different than all the rest in this same year range, so it should be a piece of cake! Yes, I jinxed myself again. I had worked with the shop owner and his tech over the phone during the previous week in an effort to help them determine what the cause of the engine misfire was. The ECM had failed to drive the fuel injector in cylinder number four anymore, which necessitated replacement of the module. The shop owner knew the replacement needed to be programmed and asked what my schedule looked like. Initially, he was ecstatic to learn he might be able to ship the car before the weekend.

By 6 p.m. that day, my laptop's battery was running low and so was my patience The programming of the “new” ECM went smoothly, without any problems. Afterwards, I tried to perform the VTD Relearn — several times, using several different methods — and still the starter would not crank the engine.

There was a displayed message on the Driver Information Center (DIC): “Starting Disabled Remove Key,” indicating the ignition key being used was incorrect, as well as the notorious P1631 DTC present in the ECM. Apologetically, I left the car right where it was and promised the shop owner I would do research over the weekend to determine what I could have been doing wrong or determine what else may be causing the problem.

When I was unable to get the car started, so they could ensure there were no other problems related to the customer complaint, it was disappointing for them as well as for me. They had to make the call to the vehicle owner, I had to leave empty handed (and with a bit less pride,) and I now had a freshly-modified schedule for my weekend plans.

Like you probably do when confronted with similar situations, I decided now would be a good time to (re)read up on the procedure that applies to this specific vehicle, just to see what may be different from the procedures I’ve already attempted. Skimming the pages, I felt indignant, firmly believing I was doing everything I was supposed to be doing. I read more carefully the next time, and the time after that, yet still did not see anything different in the procedure to relearn VTD on this car. Determined to get to the bottom of the problem, I rearranged my Monday schedule, so I could return to the CTS (and win this battle)!

Programming theft deterrent system components

GM Service Information (SI) lists three VTD Relearn methods to choose from that may apply to this vehicle:

Through the scan tool while connected to the ACDelco Service Programming System (SPS) website — called a 10-minute relearn procedure.
Using the scan tool independently of SPS — also called a 10-minute relearn procedure.
Performed without any scan tool and is called the 30-minute relearn procedure.

The correct method to choose is dependent on what part has been replaced on the vehicle, what the engine RPO (Regular Production Order) code is on the label, and whether it’s a PassKey III (PK3) system or not. Therefore, it is vitally important you follow the correct procedure to the letter when performing VTD Relearn(s) after a component replacement. It is also important you use the correct key the first time you try to do VTD Relearn. Thinking I may have been lackadaisical in my procedure the previous Friday, I paid careful attention to every detail on Monday’s return visit.

I had printed out the SI procedures for ECM replacement and for VTD Relearn, followed each one step-by-step, and with proud bravado after everything was done, announced to everyone within earshot, “Hey ya’ll! Watch this!”

Reaching my arm into the driver’s window to turn the ignition key, the vehicle did absolutely nothing! It was in the same un-learned VTD mode as it was on Friday. How embarrassing!

I knew I’d slowed down, not missed any of the steps published, yet this car refused to play by the rules.

Step back and regroup

One lesson I learned early in my career was to step away. That’s right: When you’re in so deep emotions are now affected, and your adrenalin is pumping, step away from the problem to clear your head. This technique has proved invaluable to me on numerous occasions.

I explained to the shop owner I’d done everything by the book, precisely as it was written, yet the car still would not crank. I felt it in everyone’s best interest that I come back another day with a clear head and start over. He agreed.

Later that week, after I’d researched the problem some more, I returned. This time I had print outs of two GM Technical Service Bulletins (TSBs) that I hoped may contain the solution to the problem. One (Document ID: 799170) detailed the proper procedures to follow when replacing the ECM. While discussing it with the shop owner, we concluded although certain steps were omitted, those would not have an effect on the VTD Relearn procedure. The steps not taken were regarding documenting current oil life remaining percentages, which needed to be manually entered into the replacement ECM.

The other TSB (Document ID: 879088) titled “Programming Theft Deterrent System Components” detailed the steps to follow for VTD Relearn. It was surprising to me that some of the steps listed weren’t in SI, and based on the amount of red ink used in the TSB (about 50 percent of the verbiage), there were important things to know about this system. I used this document the next time I attempted to perform the relearn — while in the presence of the shop owner — so he could see I was not skipping steps, padding my ticket purposely or delaying the completion of the job for some other reason.

Once I finished, the same message was still displayed on the DIC “Starting Disabled Remove Key”, and the same result — no starter engagement — was happening. The shop owner and I shrugged our shoulders at the same time. I said, “The gloves are coming off! This fight’s going to continue bare knuckled!”

I read and reread the TSB over and over, searching for a clue that would make this car “learn” the keys. I reinstalled the original ECM, programmed it and still had the same result afterwards, indicating the fault wasn’t with the new module. In desperation, after reinstalling the “new” module and reprogramming it yet again, I chose to quit following directions (Yes, I stopped making the selections the instructions, and TSBs said to make and started choosing methods that weren’t supposed to apply to this car).

Believe it or not, that worked! Yes, I chose different SPS selections than what the instructions called for, and I had to do a step that wasn’t listed as “required”, and that combination allowed the keys to start the car! I found I had to perform a three-part VTD Relearn:

Perform SPS VTD Relearn using 16004063 — for LY7 / LP1 Powertrain systems
Using 16004064 — for PASSKEY III system
Perform VTD Relearn using "30-minute" method.

Afterwards, clear all DTCs from all modules reporting on the network. Then the car started!

In disbelief, I went back through the SI and TSBs, just to see if maybe I’d missed where these three steps were documented but couldn’t find them anywhere. I “took a whipping” when it came time to collect for my services but felt this was a hard-earned lesson that would probably end up valuable at some point in the future.

The CTS returns

Fast forward eight months, my life was in turmoil as I was dealing with a complete loss of feelings in both hands due to severed nerves in my neck. We were caring for a terminally ill family member in our home, and several other things that were weighing heavily on my mind at the same time when the shop owner called to say he needed me to program a replacement ECM on a CTS due to an internal failure this time (P0601). Yup, it was the same shop owner and the same car.

My “free” time was at a premium when this happened. Hurriedly, I went to the shop as soon as his tech had installed the new ECM, not knowing when I’d be able to return if I didn’t address this ASAP. Wouldn’t you know I did the same procedure again? Yup, the same thing happened again (remember the old saying about fooling me?).

Having that sick feeling in my gut, knowing this had been such a miserable experience in the past, I had enough sense to stop after the first VTD Relearn attempt and got permission to review my notes from the last time (which weren’t in my possession at the time), then return.

“I am my own worst enemy.” Don’t you know I could not find where I’d saved the information from the first time I worked on this car? I was so frustrated!

I knew the shop had a responsibility to get their customer’s car back to them soon, and I had responsibilities that weren’t “work related,” both adding to the stress felt that day. There was so much happening I just couldn’t think straight, so I walked away. I got away from the problem.

That night I awoke from a sound sleep, walked over to my PC, and quickly located the file I couldn’t find the day before. Everything went like clockwork at the shop the next morning.

Quite frankly, it isn’t uncommon anymore when the procedures we have used for years simply don’t work on the vehicle we’re seeing today. Have you come across any vehicles produced with “Mid-Year” changes yet? Cars change so often that even among the same brand, the ways to accomplish something isn’t always done the same way, as evidenced by this Cadillac.

There are several poignant lessons about this case study that I feel are important to emphasize: