Is Your GM Truck or Van Running Rough?
If you’re dealing with a persistent check engine light, erratic engine behavior, a no-start condition, or failed emissions, a faulty Powertrain Control Module (PCM) is often the culprit. In my 20+ years as a technician, I’ve seen these exact issues on countless late-90s GM vehicles. The PCM is the brain of your engine, and when it fails, it can cause a cascade of frustrating problems. This isn’t just an inconvenience; it affects your vehicle’s reliability, fuel economy, and safety. You need a solution that works right out of the box, without expensive trips to the dealership.
The Direct-Fit, Programmed Solution
This is a genuine, road-tested used OEM PCM that has been meticulously inspected and is ready for service. The most critical part of the process happens before we ship: we flash the module with the latest GM-certified software specifically for your vehicle. All you have to do is provide your Vehicle Identification Number (VIN) after purchase. This ensures that all engine and transmission parameters are perfectly matched, making the installation process as simple as possible.
Common Symptoms of a Failing PCM:
- โ Check Engine Light (CEL) is on with various communication or sensor codes
- โ Engine cranks but will not start
- โ Rough or unstable idle
- โ Poor acceleration and loss of power
- โ Decreased fuel mileage
- โ Harsh or incorrect shifting from the transmission
- โ Vehicle fails emissions testing
From the Shop Floor: A Real-World Diagnosis
A customer’s 1999 GMC Savana 2500 came in last month with a baffling issue: it would run perfectly for 20 minutes, then suddenly stall and refuse to restart for an hour. No consistent codes were stored, just a generic U-code for lost communication every so often. After checking all the usual suspectsโfuel pressure, crank sensor, ignition moduleโwe focused on the PCM. On these older GM units, I’ve found that internal solder joints, particularly for the main processor, can develop micro-fractures from years of heat cycles. As the module heats up, the connection is lost. After it cools, the connection returns. Swapping in a known-good, correctly programmed PCM like this one solved the problem instantly. It’s a classic failure mode that many shops misdiagnose, costing customers time and money on unnecessary parts.
Plug-and-Play Installation: No Dealer Visit Required
Because we program the unit to your VIN, you can typically install this yourself and get back on the road. While some models may require a security relearn procedure (which can be done without special tools), this module is designed to be a direct replacement.
- Safety First: Disconnect the negative battery terminal and wait 10 minutes for any residual power to dissipate.
- Locate the PCM: On most of these trucks and vans, the PCM is located in the engine compartment, often on the driver’s side inner fender or near the battery.
- Disconnect Connectors: Carefully unlatch and remove the electrical harness connectors. Inspect them for any corrosion or bent pins and clean them if necessary.
- Remove the Old Module: Unbolt the old PCM from its mounting bracket.
- Install the New Module: Mount your new, pre-programmed PCM and securely reconnect the electrical harnesses. Ensure they click into place.
- Reconnect Battery: Reattach the negative battery terminal.
- Key On, Engine Off: Turn the key to the ‘ON’ position (without starting) for 30 seconds to allow the systems to initialize before starting the engine.
Guaranteed Compatibility for Your 1998-1999 Express 3500 PCM
This module, service number 9366810, is a direct replacement for a wide range of GM vehicles from 1998 and 1999. It is crucial to match your part number or verify fitment using the list below. This unit is compatible with service IDs 09355699, 16266645, 16250279, and 16258815. Please confirm your vehicle is on this list to ensure a perfect match.
Vehicle Fitment List:
- Cadillac Escalade: 1999
- Chevrolet Astro Van: 1998
- Chevrolet Blazer S10: 1998
- Chevrolet Express Van (1500, 2500, 3500): 1998-1999
- Chevrolet Pickup (1500, 2500, 3500): 1998-1999
- Chevrolet S10 Pickup: 1998
- Chevrolet Suburban (1500, 2500): 1998-1999
- Chevrolet Tahoe: 1998-1999
- GMC Envoy: 1998
- GMC Jimmy S15: 1998
- GMC Safari Van: 1998
- GMC Savana Van (1500, 2500, 3500): 1998-1999
- GMC Sierra Pickup (1500, 2500, 3500): 1998-1999
- GMC Sonoma S15 Pickup: 1998
- GMC Yukon: 1998-1999
- Isuzu Hombre: 1998
- Oldsmobile Bravada: 1998