Restore Your Truck’s Brain and Get Back on the Road
As a technician with over two decades of experience under the hood, I’ve seen firsthand how a failing Powertrain Control Module (PCM) can bring a perfectly good truck to a dead stop. If your 1998-1999 GMC 3500 is suffering from bizarre electrical gremlins, poor performance, or a frustrating no-start condition, the problem often lies with the vehicle’s computer. This isn’t just a part; it’s the central command center for your engine and transmission. When it fails, everything from fuel delivery to spark timing and transmission shifting can become erratic.
We’re offering a reliable, tested, and pre-programmed PCM that serves as a direct-fit replacement. This unit, part number 9355699, is a genuine used module sourced from a salvaged vehicle and meticulously prepared for its next life. The most critical step—programming—is handled by our team before it ever leaves our facility. We use your vehicle’s VIN to flash the module with the latest GM software updates, ensuring it communicates perfectly with your truck’s specific systems. This eliminates the need for an expensive trip to the dealership for programming, saving you significant time and money.
Case Study: A Tricky Diagnosis
I remember a ’99 Suburban that came into my bay with a complaint of intermittent stalling, but only after it was fully warmed up. No check engine light, no consistent codes—a real head-scratcher. After checking fuel pressure and ignition components, I suspected the PCM. On these GMT400 platforms, the PCM is mounted in the engine bay where it’s exposed to constant heat cycles. Over 20+ years, this can cause microscopic cracks in the internal circuit board. We swapped in a pre-programmed PCM, and the problem vanished. It’s a classic failure mode I’ve seen hundreds of times on these otherwise bulletproof trucks.
Is Your Truck Showing These Symptoms?
A failing PCM can manifest in numerous ways. If you’re experiencing any of the following, this module is a likely solution:
- ✔ Check Engine Light is on with codes like P0601 (Internal Control Module Memory Check Sum Error), P0604, or P0606.
- ✔ The engine cranks but refuses to start.
- ✔ Unexplained stalling, especially when the engine is warm.
- ✔ Rough or erratic automatic transmission shifting.
- ✔ A noticeable drop in fuel economy.
- ✔ Communication errors with your scan tool.
- ✔ The anti-theft or security light stays on, preventing startup.
A Straightforward Guide to Installation
For the confident DIYer or professional mechanic, installing this PCM is a direct process. Since we handle the programming, you won’t need any special scan tools for that step.
- Safety First: Disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent accidental contact.
- Locate the PCM: On most of these trucks and vans, the PCM is located in the engine compartment, typically on the driver’s side fender well or near the battery.
- Disconnect the Connectors: Carefully unlatch and remove the electrical harness connectors from the old PCM. Inspect the connectors for any corrosion or damaged pins.
- Remove the Old Module: Unbolt the old PCM from its mounting bracket. Keep the hardware as you will reuse it.
- Install the New Module: Mount your new, pre-programmed PCM onto the bracket and securely fasten it.
- Reconnect Everything: Plug the electrical connectors firmly into the new PCM until they click into place. Reconnect the negative battery terminal.
- Perform Security Relearn: You will need to perform a security relearn procedure. 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. This allows the vehicle’s security system to recognize the new PCM. Your truck will not start until this is completed.
Verified Vehicle Compatibility
This module is a guaranteed fit for a wide range of GM vehicles that use service number 9355699. Please verify your original part number or consult the list below. This part is compatible with numbers 09355699, 16266645, 16250279, 16258815, 09366810, and 9366810.
CHEVROLET 2500 PICKUP 98-99 (Gasoline)
CHEVROLET 3500 PICKUP 98-99 (Gasoline)
GMC 1500 PICKUP 98-99 (Gasoline)
GMC 2500 PICKUP 98-99 (Gasoline)
GMC 3500 PICKUP 98-99 (Gasoline)
CADILLAC ESCALADE 99
CHEVROLET SUBURBAN 1500/2500 98-99 (Gasoline)
CHEVROLET TAHOE 98-99 (Gasoline)
GMC YUKON 98-99
CHEVROLET ASTRO 98
GMC SAFARI 98
CHEVROLET EXPRESS 1500/2500/3500 VAN 98-99 (Gasoline)
GMC SAVANA 1500/2500/3500 VAN 98-99 (Gasoline)
OLDSMOBILE BRAVADA 98 (w/o build date opt ZN4)
CHEVROLET BLAZER S10 98 (w/o build date opt ZN4)
GMC JIMMY S15 98 (w/o build date opt ZN4)
GMC ENVOY 98 (w/o build date opt ZN4)
CHEVROLET S10 PICKUP 98 (4.3L, w/o build date opt ZN4)
GMC SONOMA 98 (4.3L, w/o build date opt ZN4)
ISUZU HOMBRE 98 (4.3L, w/o build date opt ZN4)
Frequently Asked Questions
Frequently Asked Questions
Why do you need my VIN?
Your Vehicle Identification Number (VIN) is essential. It allows us to program the PCM with the exact software and calibrations for your truck’s engine, transmission, and options. This ensures seamless communication and proper function right out of the box.
Is this a new part?
No, this is a high-quality, tested used part sourced from a salvaged vehicle. Each unit is inspected and verified to be fully functional before being programmed and shipped. This provides a reliable and cost-effective solution.
Will my truck start immediately after installation?
No. After installing the PCM, you must perform a security relearn procedure (also known as a CASE relearn). This syncs the new module to your vehicle’s anti-theft system. It’s a simple procedure that takes about 30 minutes and does not require special tools.
Do I need to send my old PCM (core) back?
No core charge or return is required for this part. You can keep or dispose of your old module.
How do I find my part number?
The part number is printed on a sticker on the PCM itself. You will need to locate the module on your vehicle and read the service number (SERV. NO.) from the label to confirm a match.