Restore Your Truck’s Performance and Reliability
Is your Silverado 3500 suffering from frustrating issues like a persistent check engine light, erratic shifting, or a no-start condition? The Powertrain Control Module (PCM), the electronic brain of your truck’s engine and transmission, is often the source of these problems. This replacement PCM, part number 12602801, is the definitive solution to get your workhorse running smoothly again. We take the guesswork and hassle out of the repair by professionally programming the module to your vehicle’s specific VIN with the latest GM software updates before it even ships. This means no expensive trips to the dealership for programming—it’s ready to install right out of the box.
From the Diagnostic Bay: The Ghost in the Machine
I had a 2006 Silverado 2500 with the 8.1L in my bay that was driving the owner crazy. It would randomly fail to start, but only after it was hot. Other times, the transmission would slam into gear. There were no consistent trouble codes, just a few intermittent U0100 (Lost Communication with ECM/PCM) codes stored in other modules. After checking all the power and ground circuits to the PCM—a critical first step—we found they were solid. The issue was internal to the module itself. Heat was causing a hairline fracture on the circuit board to expand, breaking the connection. A replacement, pre-programmed PCM like this one solved the problem permanently. These intermittent issues are classic signs of a failing computer.
Common Signs of a Failing PCM
If you’re experiencing any of the following, a faulty PCM is a likely culprit. In my 20+ years of experience, these are the symptoms I see most often with these GM modules.
- ✔ Check Engine Light is illuminated with codes like P0601 (Internal Control Module Memory Check Sum Error) or P0606 (ECM/PCM Processor Fault).
- ✔ The engine cranks but refuses to start.
- ✔ Poor or declining fuel economy.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ The engine stalls, stumbles, or misfires intermittently.
- ✔ Failure to pass an emissions inspection.
- ✔ Loss of communication with the scan tool or other modules (U-codes).
A Straightforward Guide to Installation
Replacing the PCM on your Silverado is a manageable job for a DIYer. Follow these steps carefully to ensure a smooth installation. The module is typically located in the engine bay, under the battery tray on the driver’s side.
- Safety First: Disconnect the negative terminal from your truck’s battery and secure it away from the post to prevent any accidental reconnection.
- Access the Module: You will likely need to remove the battery and the battery tray to gain access to the PCM. Keep track of all bolts and hardware.
- Disconnect Connectors: Carefully unplug the electrical connectors from the old PCM. There are typically release tabs that need to be depressed. Inspect the connectors for any corrosion or damage before proceeding.
- Remove Old PCM: Unbolt the old module from its mounting bracket and remove it from the vehicle.
- Install New PCM: Mount your new, pre-programmed PCM into the bracket and reconnect the electrical connectors. Ensure they click securely into place.
- Reassemble: Reinstall the battery tray and the battery. Reconnect the negative battery terminal.
- Perform Security Relearn: This is a critical final step. Your truck’s anti-theft system needs to sync with the new PCM. The standard procedure is to turn the key to the ‘ON’ position (without starting) for 10-15 minutes, then turn it ‘OFF’ for 10 seconds. Repeat this cycle three times. On the fourth attempt, the truck should start.
Guaranteed Fitment for Your GM Vehicle
This module is a direct replacement for part numbers 12589462, 12602801, and 89017749. It is confirmed to fit the following vehicles. Please verify your specific model and options.
AVALANCHE 2500 05-06 (LH front under battery)
BLAZER S10/JIMMY S15 05 (RH front engine compartment)
CTS 04-05 V-Series (ID 12589462 or 12602801)
EXPRESS/SAVANA 1500 VAN 05-07 (LH rear engine compartment)
EXPRESS/SAVANA 2500 VAN 05-07 (Gasoline, LH rear engine compartment)
EXPRESS/SAVANA 3500 VAN 05-07 (Gasoline, LH rear engine compartment)
SAFARI (GMC) 05 (LH front by battery)
SIERRA/SILVERADO 1500 PICKUP 05-07 (Classic style, 4.3L, w/o hybrid)
SIERRA/SILVERADO 2500 PICKUP 05-07 (Classic style, 8.1L Gasoline)
SIERRA/SILVERADO 3500 PICKUP 05-07 (Classic style, 8.1L Gasoline)
SUBURBAN 2500 05-06 (8.1L)
YUKON XL 2500 05-06 (8.1L)
Frequently Asked Questions
Frequently Asked Questions
What information do you need to program my PCM?
After you complete your purchase, you will need to provide us with your vehicle’s 17-digit Vehicle Identification Number (VIN). We use this to load the exact GM-specified software for your truck’s configuration.
Is this part difficult to install?
For someone with basic mechanical skills, it is a straightforward process. The main steps involve disconnecting the battery, swapping the module, and performing a security relearn procedure. Please see our installation guide above.
Do I need to take my truck to a dealer after installation?
No. Because we program the module to your VIN before shipping, you do not need a dealership visit for programming. You will, however, need to perform the simple security relearn procedure outlined in our guide.
Where is the PCM located on a 2005-2007 Silverado 3500?
On most Silverado and Sierra HD trucks from this era, the PCM is located in the engine compartment on the driver’s side, underneath the battery and battery tray.
Will this fix my transmission shifting problems?
In many cases, yes. The PCM controls both engine functions and transmission shift points. If the module is failing, it can cause harsh or erratic shifting, and a new, correctly programmed PCM will resolve these issues.