Is Your 2006 Trailblazer EXT Running Rough or Not Starting?
As a technician with over two decades of experience, I’ve seen countless GMT360 platform vehicles like your 2006 Trailblazer EXT come into the shop with baffling issues. The owner might complain about a sudden no-start condition, a check engine light that won’t go away, erratic shifting, or terrible fuel mileage. These symptoms can send you down a rabbit hole of changing sensors and parts, but often, the root cause is the one component controlling everything: the Powertrain Control Module (PCM).
Common Symptoms of a Failing PCM on a 4.2L Trailblazer:
- Complete no-start or crank-no-start condition
- Check Engine Light (CEL) with communication error codes (e.g., U-codes)
- Harsh or delayed transmission shifting
- Poor engine performance and significantly reduced fuel economy
- Stalling at idle or while driving
- Inability for a scan tool to communicate with the module
A Real-World Diagnosis Story
A customer’s 2006 GMC Envoy with the 4.2L engine (a sibling to your Trailblazer) came in on a tow truck last month with a classic crank-no-start issue. The owner had already replaced the battery and checked the fuel pump. When we connected our diagnostic scanner, it couldn’t establish a link with the PCM. This is a huge red flag. After verifying the power and ground circuits to the module were intact, we knew the PCM itself had failed internally. This is a common failure I’ve diagnosed hundreds of times on these vehicles; the internal circuit boards and processors simply wear out over time, leading to a complete communication breakdown.
The Simple, Reliable Solution: A VIN-Programmed PCM
This is a direct-fit replacement Powertrain Control Module for your vehicle. The most significant benefit we offer is that this isn’t just a part in a box. Before we ship it, we will program it with the latest official GM software calibration specifically for your truck using the Vehicle Identification Number (VIN) you provide. This critical step ensures that the computer works seamlessly with your engine, transmission, and all related systems, including the anti-theft (Passlock) system. You get a module that is truly ready for installation, saving you a trip to the dealership and the high cost of their programming services.
Guaranteed Fitment and Compatibility
This PCM, identified by part number 12569773, is the correct replacement for a wide range of GM vehicles. It directly interchanges with the following part numbers:
12588650, 12589311, 12589585, 12591647, 12591648, 12593531, 12593532, 12594430, 12594431, 12596783, 12596784, 12597521, 12597776, 12597777, 12600818, 12604438, 12604439, 12606369, 12606373, 12606374, 12606398, 12606399, 19209820, 19209821
This module fits the following vehicles:
- 2006 TRAILBLAZER / TRAILBLAZER EXT (4.2L Engine, LH Engine Location)
- 2006 ENVOY / ENVOY XL (4.2L Engine, LH Engine Location)
- 2006 RAINIER (4.2L Engine, LH Engine Location)
- 2006 ISUZU ASCENDER (4.2L Engine, LH Engine Location)
- 2006 SAAB 9-7X (6 Cylinder, ID 12569773 or 12597521, LH Engine Location)
- 2004-2006 COLORADO / CANYON (RH Firewall Location)
- 2006 HUMMER H3 (RH Firewall Location)
- 2006 ISUZU I-280 / I-350 (RH Firewall Location)
The installation is straightforward for a DIYer with basic tools. Simply disconnect the battery, locate the old PCM on the driver’s side of the engine, carefully unplug the wiring harnesses, unbolt the module, and install the new one in its place. Once reconnected, your vehicle will have its brain back, operating on the newest software for optimal performance and reliability.