Is your Pontiac Montana or other GM vehicle running rough, stalling unexpectedly, or showing a persistent Check Engine Light? As a technician with over two decades of diagnostic experience, I’ve seen how a failing Powertrain Control Module (PCM) can cause a cascade of frustrating and hard-to-diagnose issues. This isn’t just a part; it’s the brain of your engine and transmission, and when it falters, your vehicle’s reliability suffers. This replacement PCM, part number 89017735, is the definitive solution to restore your vehicle’s performance and peace of mind.
We take the guesswork and high cost out of the repair. Unlike a generic module from a parts store, this unit arrives at your door pre-programmed with the latest official GM software updates. All we need is your vehicle’s VIN at checkout. This critical step ensures the PCM communicates perfectly with your specific vehicle’s systems—from the fuel injectors to the transmission shift points—for a seamless, effective repair. By installing this professionally programmed 2003-2005 Montana PCM, you’re not just replacing a part; you’re restoring the precise operational parameters designed by the manufacturer.
Case Study: The Phantom Misfire
I remember a 2004 Pontiac Montana that came into the shop with an intermittent misfire and a P0300 (Random/Multiple Cylinder Misfire) code that just wouldn’t quit. The owner had already replaced the spark plugs, wires, and even the ignition coil pack, but the problem persisted, especially on damp mornings. After hooking up the scope and monitoring the injector pulse width, I noticed erratic signals that didn’t correspond to engine load. The culprit wasn’t a mechanical fault but a failing PCM. The internal drivers were breaking down under certain temperature conditions. We installed a VIN-programmed module just like this one, and the Montana ran perfectly. It’s a classic example of how the PCM can mimic other failures, costing owners time and money on unnecessary parts.
Is Your Vehicle Showing These Symptoms of a Bad PCM?
A faulty PCM can manifest in many ways. If you’re experiencing any of the following, this module is likely the solution you need. Keep an eye out for:
- ✔ Check Engine Light is on with codes like P0601, P0602, P0605, or U-series communication codes.
- ✔ The engine cranks but refuses to start.
- ✔ Unexplained drops in fuel economy.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ The vehicle stalls for no apparent reason, either at idle or while driving.
- ✔ Noticeable loss of engine power and poor acceleration.
- ✔ Failure to pass state emissions testing.
A Straightforward Guide to Installation
Replacing the 2003-2005 Montana PCM is a job most DIYers can handle with basic tools. The location can vary slightly by model (check the fitment list), but it’s often found in the engine compartment, typically inside the air filter box housing for protection.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and wait at least 10 minutes to allow capacitors to discharge.
- Locate the Module: On most of these vans and cars, the PCM is located on the driver’s side of the engine compartment, attached to or inside the air cleaner assembly.
- Disconnect Connectors: Carefully unclip the wiring harness connectors. These GM connectors often have a locking tab or lever. Do not force them; look for the release mechanism.
- Remove the Old PCM: Unbolt the module from its mounting bracket. It’s typically held by a few small bolts or nuts.
- Install the New PCM: Mount your new, pre-programmed module in place and securely tighten the bolts.
- Reconnect Everything: Plug the wiring harnesses back in until they click, ensuring a solid connection. Reconnect the negative battery terminal.
- Final Step (Important): Some vehicles may require a security relearn procedure, which can often be done without a scan tool by cycling the key. Consult your vehicle’s service information for specific steps if it doesn’t start immediately.
Verified Vehicle Compatibility
This module is a direct-fit replacement for a wide range of General Motors vehicles. Please verify your model and year below. This unit is compatible with original part numbers 12583827 and 12583826.
AZTEK 03-05
BONNEVILLE 04-05 (3.8L)
CENTURY 03-05
GRAND AM 03-05 (3.4L)
GRAND PRIX 03 (3.1L)
IMPALA 03-05 (3.4L)
LESABRE 04-05
MALIBU 03 (Classic Body Style)
MONTE CARLO 03-05 (3.4L)
MONTANA 03-05
PARK AVENUE 04-05
RENDEZVOUS 03-05
SILHOUETTE 03-04
VENTURE 03-05
Note: Some models may have specific ID requirements. Providing your VIN ensures we send the correctly programmed unit for your exact vehicle configuration.
Frequently Asked Questions About Your New PCM
Frequently Asked Questions
What exactly is a PCM?
The Powertrain Control Module (PCM) is your vehicle’s main computer. It controls all aspects of engine and transmission function, from fuel mixture and ignition timing to emission controls and transmission shifting, to ensure optimal performance and efficiency.
Why is providing my VIN so important?
Your Vehicle Identification Number (VIN) allows us to program the module with the precise software for your car’s specific engine, transmission, and options. This step is crucial for a successful, error-free installation and prevents compatibility issues.
Will this fix my check engine light?
If the check engine light is caused by an internal failure of the PCM (common codes include P0601-P0606), then yes, this replacement part will solve the problem. It’s always best to have the codes read to confirm the diagnosis before ordering.
Is this part difficult to install myself?
For most DIYers with basic hand tools, this is a very manageable job. Since the module comes pre-programmed, you avoid the most difficult step. Just follow our installation guide, and you can have your vehicle running properly again in about an hour.
What is the difference between a PCM and an ECM?
The terms are often used interchangeably. ECM (Engine Control Module) typically only controls engine functions. PCM (Powertrain Control Module) is more common in modern vehicles and controls both the engine and the automatic transmission. This part functions as the PCM for the listed vehicles.