2005 Classic possible ignition switch problem

This is kinda a long story, but I'll try to keep as short as possible.
The vehicle I've had since 2007. It has just over 90k miles. Body wise it's the best I've had with little rust, it's kept in a unheated garage for all the years I have had it. I only put on 2-3k miles a year. I've had some problem with ti, but nothing really major until now. I don't want to sell it and find a replacement with all the hassle involved in spite of the low current value of the car..
Last week. one day it started as usual, the next day it just cranked, no start. Tried a lot of troubleshooting for days ( ICM testing, fuel pressure etc.) with what turned out to be everything except the problem; the Theft system. https://chevroletforum.com/forum/images/smilies/eek.gif Never encountered this before, virgin territory for me.

I have a OTC scan tool, but it is somewhat limited since it doesn't have History ability. A family member has access to a Snap-On $8k scan tool that does have that ability and a ton of everything else. He also has far more experience than I do since it's kinda a hobby for him other than working in the industry. Initially no codes showed as it was with my scanner. After numerous tries at cranking, a B3031 code showed. He then looked for the history and a B2960 showed. He cleared that code and the vehicle started.

We tried a 2nd start and that worked. I planned on going to a recommended independent shop, but they don't do this type of repair, thou he did recommend another very highly, but after I described the situation about the DTC being cleared, he said they couldn't work on it with no code. I contacted the local Chevy dealer and basically told the same thing thou I did stop in at their parts dept. to check prices and availability of the parts (cylinder and switch) and both were available, but the BCM that controls the function has been discontinued. https://chevroletforum.com/forum/images/smilies/frown.gif

Now I have a 'time bomb' not knowing when or if this will happen again unless I just ok a replacement of both parts and the assumption that is the actual problem. It's gone thru about 6 'starts' so far (I tried to get it to fail by doing 3 or 4 test starts waiting at the dealer).

Attached are scans of the two trouble codes for reference from the factory service manual. What do you guys think??

About 10 years ago (May of '13) I worked on an '05 Malibu Classic with similar symptoms - I keep notes. Here is what I had in the record:

"Replaced ignition switch; Re-installed original PCM; Removed IP and re-seated switch connector; Taped wire harnesses repairing failed cloth; Re-learned Passkey to BCM/PCM."

It was exhibiting a crank with no injector pulses (theft mode). Someone else had replaced the PCM thinking it was at fault. I handed that back to the owner suggesting he get a refund. The sensing ring on the switch was not reliably sending a signal to the PCM, possibly due to wiring and connection issues, possibly due to weak magnets/coils in the switch. That problem never occurred again.

I understood there are 2 parts to the ignition switch/cylinder assembly. Was it the actual switch, or the cylinder??

I assume "IP" is the instrument panel? :confused:

Which Passlock system does this use 1 or 2?

IP is the instrument panel, including the plastic lower bolster hiding everything in the rest of the dash. By my recollection, there is a harness connection forward of the lower bolster for the switch and collar, just as there is for about everything else on the steering column. There was also a goofy mechanical interlock cable to floor shifter if memory serves me. The instrument cluster, radio, HVAC control, and other parts had to be removed to access the ignition switch and wiring.

The problem in this case was not the lock cylinder but the position sensing ring/collar surrounding it, part of the ignition electrical switch and PassLock sensor system.

I believe the 2005 model used the original PassLock system, not the "II" or "III" versions.

From what I remember reading along the way it's the Passcode II version.


Some unknown action/occurrence triggered a DTC that couldn't be created again, somewhere between the ignition key assembly (my term) and the BCM.
I found there are two ways to defeat this "Threat Deterrent" system; one via a resistor across the black & yellow leads, the other by a toggle switch jumping the yellow lead. I choose the on-off toggle switch since I can re-enable it if needed for inspection or if some other issue surfaces (which so far hasn't).


I can't believe the number of 'hits' I found when I searched for the solution including all the horror stories of owners left stranded because of a lame so called theft/security system. :jerking:

Yes, there is something in the manual (at the very end) which few actually read. I do, but never remember seeing it and actually forgetting about the feature. In 45 years, I've never had my car stolen. But I've been stranded before (for other reasons) and it's not fun.

Be cautious about the accuracy of any internet advice and information (including mine).

Systems with the two-wire harness using a resistance to sense the correct ignition key were VATS and "Passkey II" systems, VATS (Passkey) used a resistance pellet embedded in the key. That began in 1984. That changed design a couple times to transition to the PassKey III using an RFID-type tag in the key bow and transponder antenna surrounding the switch assembly.

The "Passlock" systems are also of multiple varieties, mostly using a proximity detector to verify that the lock cylinder has not been forced and/or the wiring jumpered. The system can be "fooled" once to allow a start, but the BCM will be looking for the key/lock sensor signal to transition (from on to off, and back to on for the next start attempt) when the engine is turned off so a permanent resistor (or Shottkey diode) may not work more than once.

When I searched for a solution, this procedure came up multiple times, all stated the same basic procedure. That 'resistor' method, I dismissed due to the 'unknown' exact value of the resistor and the fact it's not easily 'undone'.
The 'toggle switch' can re-enable the function if needed with that switch hanging down behind the 'floor shift' housing, next to the drivers right leg (not interfering with driving what so ever).


It's just it was a SOB to re-position that ignition cylinder assembly so I could even reach the three wire taped bundle.

Your description of the "fun" is probably why I still remember working on that one, even thought it was years in the past.