GM Repair Questions? Ask a Mechanic for Answers ASAP
Hello and welcome to Just answer.com, Super mechanic here. About your vehicle.
When there are no trouble codes to go by and the system has to be relearned more than one or two times, what I do is replace the ignition lock cylinder, (with the passkey sensor in it) and that seems to work out most of the time.
Of course, you will want to get the new cylinder from the dealer and have it coded to your original key and then do the relearn on it.
You must perform a theft relearn procedure if any of the following components have been replaced:
The above modules, with the exception for the Passlock Sensor must also be programmed with each module's own vehicle configuration.
The BCM and the PCM will learn the new code on the next start attempt.
If the engine starts then it is getting the correct reading from the passkey sensor. You can only relearn it when it is not starting. If you encounter the problem then you can do it yourself, but you may want to see if he/she will replace the lock cylinder for free or a discount to you.
The vehicle theft deterrent system is designed in order to prevent vehicle theft by disabling the fuel injectors unless the lock cylinder is correctly engaged by a mechanical key. The theft deterrent system uses the following 4 components for theft prevention:
When starting the engine, the PCM searches for a password XXXXX the BCM through the Class 2 serial data circuit. If the password XXXXX XXXXX recognized or not present, the PCM will disable the engine. Two modes of tamper detection are provided:
After the vehicle has passed theft detection, the PCM will continue normal operation.Ignition Switch The mechanical key and lock cylinder is located in the instrument panel assembly. The electrical switching portion of the assembly is separate from the key and lock cylinder. Both of the components are synchronized and work in conjunction through the action of the actuator rod assembly.Passlock Lock Cylinder The Passlock lock cylinder is a locking cylinder that turns a rotating magnet past a stationary hall effect sensor. This action creates the Pass/key cylinder data. The Passlock cylinder data is sent to the Body Control Module (BCM). The Passlock lock cylinder is interfaced with the BCM via a 3-wire connection:
Powertrain Control Module (PCM) The Powertrain Control Module (PCM) is located on the lower left side of the instrument panel.The PCM communicates with the Body Control Module (BCM) via serial data over the class 2 serial data bus, CKT 1807. When the BCM determines a passed theft condition, the BCM sends a coded password XXXXX the PCM. When the PCM receives the correct password, the PCM enables the fuel injection system, allowing the vehicle to operate correctly. The PCM may allow the car to start and quickly stall during a failed theft condition.The following conditions may cause the PCM to enter a tamper mode:
If the BCM does not receive a password XXXXX a preset time window, the BCM will enter a short tamper mode. During this mode, the PCM will not allow the car to operate for 4 seconds. If the password XXXXX XXXXX the PCM will enter the long tamper mode. In the long tamper mode, the following actions will occur:
Although the vehicle may start, the engine will quickly stall due to a fuel cut-off.In the event of an open in the serial data communication between the BCM and the PCM, the following actions occur:
If a failure occurs in serial data before the ignition cycle, while the PCM is not fail-enabled, the PCM will never receive a valid password XXXXX order to enable the continued use of the fuel injectors.
No problem, our goal is to help save you money, (not to mention some headaches)
I had a few that would do that same thing when they were fairly new and after the first (tow bill) the shop forman said, "replace the ignition lock cylinder" and then they were fixed. Some sort of internal thing with the passkey sensors, is what we determined.
I will be going to lunch, (hope n) but let me know if you need anything, I'm normally always workin' but later tonight I will be spending time with my little ones, (yep, I still have little ones, 12 and 14..at my age, LOL) I will prolly bring my laptop for when they get glued to the TV.