Restore Peak Performance and Reliability to Your GM Truck or SUV
Is your 2003 Trailblazer EXT or other GM vehicle suffering from frustrating issues like a persistent Check Engine Light, poor fuel mileage, or a no-start condition? As a technician with over two decades of experience under the hood, I’ve seen countless drivers chase expensive and incorrect repairs when the real culprit is a failing Powertrain Control Module (PCM). This module, part number 12602802, is the central computer for your engine. When it falters, it can cause a cascade of problems that are often misdiagnosed.
Case Study: The Ghost in the Machine
I remember a 2004 Silverado that came into my bay. The owner had already replaced the battery, alternator, and fuel pump trying to solve an intermittent no-start and stalling problem. His scan tool would occasionally lose communication, and he was at his wit’s end. After a quick diagnostic check, I suspected the PCM. The internal processor was failing, causing unpredictable communication drops and erratic engine commands. We installed a VIN-programmed PCM just like this one, performed the security relearn, and the truck ran perfectly. It’s a classic scenario where tackling the root cause—the vehicle’s brain—saves hundreds in unnecessary parts and labor.
Is Your GM Vehicle Showing These Signs of PCM Failure?
A failing PCM can manifest in various ways. If you’re experiencing any of the following, this module is the likely solution. Keep an eye out for these common symptoms:
- ✔ Check Engine Light: Often with internal module error codes like P0601, P0602, P0606, or communication codes like U0100.
- ✔ No-Start or Hard Starting: The engine cranks but won’t turn over, or takes an unusually long time to start.
- ✔ Poor Drivability: Experiencing rough idling, engine stalling, hesitation during acceleration, or harsh transmission shifting.
- ✔ Decreased Fuel Economy: A sudden and unexplained drop in your vehicle’s MPG.
- ✔ Failed Emissions Test: The PCM controls the emissions system, and a fault will prevent you from passing inspection.
- ✔ Communication Errors: Your mechanic’s scan tool is unable to communicate with the PCM.
The Smart Solution: VIN-Programmed and Ready to Install
The biggest hurdle in replacing a PCM has always been the expensive and time-consuming programming required at a dealership. We eliminate that step completely. When you purchase this 2003 Trailblazer EXT PCM, we flash it with the latest official GM software updates using the Vehicle Identification Number (VIN) you provide. This ensures that the module is perfectly matched to your vehicle’s specific configuration, including engine, transmission, and emissions equipment. It arrives at your door ready for a straightforward installation, saving you time and money.
A Straightforward Guide to Installation
Installing your new PCM is a manageable job for a DIY enthusiast. While locations vary slightly, the process is generally the same for most compatible GM trucks and SUVs.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and wait about 10 minutes to ensure all systems are powered down.
- Locate the PCM: On most models like the Silverado, Tahoe, and Suburban, the PCM is found in the engine bay on the driver’s side, often under or next to the battery tray. On models like the Trailblazer EXT, it’s typically located next to the air filter box.
- Disconnect the Old Module: Carefully unplug the electrical connectors. These usually have a locking tab or lever that needs to be released. Never force them.
- Swap the Modules: Unbolt the old PCM from its mounting bracket and secure the new one in its place.
- Reconnect Everything: Plug the electrical connectors firmly into the new PCM until they click into place. Reconnect the negative battery terminal.
- Perform Security Relearn (CRITICAL): You must perform a security relearn procedure to sync the new PCM with your vehicle’s anti-theft system. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then ‘OFF’ for 10 seconds, and repeating this cycle three times. Your vehicle will not start until this is completed.
Verified Vehicle Compatibility
This module is a direct replacement for service number 12602802 and is compatible with several other service numbers, including 89017750, 12582605, 12589463, 89017734, and 28042802. It fits a wide range of GM models. Please verify your vehicle, year, and engine options below.
ESCALADE 04 Electronic Control Module; (LH front under battery), ID 12602802
ESCALADE EXT 04 Electronic Control Module; (LH front under battery), ID 12602802
HUMMER H2 04 Electronic Control Module; (LH front under battery), SUV
SIERRA 3500 PICKUP 03 Electronic Control Module; (LH front under battery), gasoline, 6.0L
TAHOE 04 Electronic Control Module; (LH front under battery), ID 12602802
YUKON XL 2500 04 Electronic Control Module; (LH front under battery), 6.0L, ID 12602802
ENVOY XL 03 Electronic Control Module; 5.3L (next to air box)
SUBURBAN 2500 03 Electronic Control Module; (LH front under battery), 6.0L
YUKON 04 Electronic Control Module; (LH front under battery), ID 12602802
YUKON XL 2500 05-06 Electronic Control Module; (LH front under battery), 6.0L
AVALANCHE 1500 04 Electronic Control Module; (LH front under battery), ID 12602802
SIERRA 1500 PICKUP 07 Electronic Control Module; classic style (creased door skin), (LH front under battery), w/o hybrid option; w/o 4.3L
SIERRA DENALI 05-06 Electronic Control Module; (LH front under battery)
SUBURBAN 2500 04 Electronic Control Module; (LH front under battery), 6.0L, ID 12602802
YUKON XL 1500 03 Electronic Control Module; (LH front under battery)
YUKON XL 1500 04 Electronic Control Module; (LH front under battery), ID 12602802
ESCALADE ESV 03 Electronic Control Module; (LH front under battery), PCM
ESCALADE ESV 04 Electronic Control Module; (LH front under battery), ID 12602802
HUMMER H2 07 Electronic Control Module; (LH front under battery), powertrain control
SIERRA 3500 PICKUP 05-06 Electronic Control Module; (LH front under battery), gasoline, 6.0L
SIERRA DENALI 03 Electronic Control Module; (LH front under battery)
SILVERADO 2500 PICKUP 05-06 Electronic Control Module; (LH front under battery), gasoline, 6.0L
SUBURBAN 1500 03 Electronic Control Module; (LH front under battery)
HUMMER H2 05-06 Electronic Control Module; (LH front under battery)
SIERRA 2500 PICKUP 04 Electronic Control Module; (LH front under battery), gasoline, 6.0L, ID 12602802
YUKON 03 Electronic Control Module; (LH front under battery)
ESCALADE 05-06 Electronic Control Module; (LH front under battery)
ESCALADE ESV 05-06 Electronic Control Module; (LH front under battery)
AVALANCHE 1500 03 Electronic Control Module; (LH front under battery)
SILVERADO 2500 PICKUP 03 Electronic Control Module; (LH front under battery), gasoline, 6.0L
SILVERADO 1500 PICKUP 04 Electronic Control Module; (LH front under battery), w/o hybrid option; w/o 4.3L; ID 12602802
TAHOE 03 Electronic Control Module; (LH front under battery)
TAHOE 05-06 Electronic Control Module; (LH front under battery)
YUKON 05-06 Electronic Control Module; (LH front under battery)
SILVERADO 3500 PICKUP 04 Electronic Control Module; (LH front under battery), gasoline, 6.0L, ID 12602802
SILVERADO 2500 PICKUP 07 Electronic Control Module; classic style (creased door skin), (LH front under battery), gasoline, 6.0L
SUBURBAN 1500 04 Electronic Control Module; (LH front under battery), ID 12602802
ISUZU ASCENDER 03 Electronic Control Module; (LH engine), 5.3L
SIERRA 1500 PICKUP 03 Electronic Control Module; (LH front under battery), w/o 4.3L
ESCALADE 03 Electronic Control Module; (LH front under battery), PCM
SSR 03 Electronic Control Module; (next to air box)
SIERRA DENALI 07 Electronic Control Module; classic style (creased door skin), (LH front under battery)
SUBURBAN 1500 05-06 Electronic Control Module; (LH front under battery)
TRAILBLAZER EXT 03 Electronic Control Module; 5.3L (next to air box)
SILVERADO 1500 PICKUP 05-06 Electronic Control Module; (LH front under battery), w/o hybrid option; w/o 4.3L
SILVERADO 1500 PICKUP 07 Electronic Control Module; classic style (creased door skin), (LH front under battery), w/o hybrid option; w/o 4.3L
SILVERADO 3500 PICKUP 07 Electronic Control Module; classic style (creased door skin), (LH front under battery), gasoline, 6.0L
YUKON XL 1500 05-06 Electronic Control Module; (LH front under battery)
ESCALADE EXT 05-06 Electronic Control Module; (LH front under battery)
SUBURBAN 2500 05-06 Electronic Control Module; (LH front under battery), 6.0L
HUMMER H2 03 Electronic Control Module; (LH front under battery)
SIERRA 2500 PICKUP 07 Electronic Control Module; classic style (creased door skin), (LH front under battery), gasoline, 6.0L
SIERRA 3500 PICKUP 07 Electronic Control Module; classic style (creased door skin), (LH front under battery), gasoline, 6.0L
SIERRA DENALI 04 Electronic Control Module; (LH front under battery), ID 12602802
YUKON XL 2500 03 Electronic Control Module; (LH front under battery), 6.0L
Frequently Asked Questions
Do I need to have this PCM programmed?
No. We handle all the programming for you before shipment. Simply provide your vehicle’s VIN during checkout, and it will arrive ready to install with the latest GM software.
What is the security relearn procedure?
It’s a required step to sync the new PCM to your vehicle’s anti-theft system. It’s a simple process you can do yourself with just the ignition key and does not require any special tools. Instructions are included above.
Is this the same as an ECM?
Yes, the terms Powertrain Control Module (PCM) and Engine Control Module (ECM) are often used interchangeably for this component. It is the main computer that controls engine functions.
Will this fix my specific check engine light code?
This module is the direct solution for internal processor failure codes like P0601 or P0606. If your code is for a specific sensor, that sensor should be tested first. However, a faulty PCM can sometimes cause false sensor codes.
What information do you need from me?
After you purchase, we will need your 17-digit Vehicle Identification Number (VIN) to program the module correctly for your vehicle’s specific build.