Get Your GM Truck or Van Running Right Again
Is your trusty Chevrolet Astro, Express van, or GMC pickup suddenly acting up? If you’re dealing with frustrating issues like a no-start condition, erratic engine performance, or a persistent Check Engine light, the problem might be the very brain of your vehicle: the Powertrain Control Module (PCM). As a technician with over two decades of experience under the hood, I’ve seen countless vehicles sidelined by a faulty computer. This isn’t just an inconvenience; it affects your work, your family, and your peace of mind. That’s why we offer a straightforward, reliable solution.
This is a quality, tested used OEM PCM, part number 09355699, sourced from a salvaged vehicle. The real value here is our professional programming service. Before we ship it, we flash the module with the latest official GM software, tailored specifically to your vehicle’s VIN. This means no expensive trips to the dealership for programming. It arrives at your door ready to install, making this a cost-effective and efficient repair for both seasoned mechanics and dedicated DIYers.
Is Your GM Vehicle Showing These Signs of PCM Failure?
A failing computer can cause a wide range of confusing symptoms. If you’re experiencing any of the following, a faulty PCM is a likely culprit. I’ve often seen these manifest as internal processor errors, leading to codes like P0601, P0605, or P0606.
- ✔ Engine cranks but refuses to start.
- ✔ Unexplained stalling or rough idling, especially after warming up.
- ✔ Harsh or erratic automatic transmission shifting.
- ✔ A significant drop in fuel economy.
- ✔ Check Engine Light is on, but the codes point to multiple, unrelated sensors.
- ✔ No communication between your scan tool and the PCM.
- ✔ The anti-theft or security light stays on, preventing the engine from starting.
A Technician’s Notebook: The Misleading Sensor Code
I remember a 1999 Chevy Suburban that came into the shop with a persistent throttle position sensor (TPS) code. The owner had already replaced the TPS twice with no luck. The engine idled poorly and had no power. Instead of just replacing the sensor again, I checked the 5-volt reference signal at the TPS connector. It was only reading 2.1 volts. Tracing it back, the issue wasn’t the sensor or the wiring; the 5V reference circuit inside the original PCM was failing. This is a classic internal failure on these modules. We installed a correctly programmed PCM, and the truck ran perfectly. It’s a prime example of how a bad computer can send you chasing ghosts—this replacement part solves the root problem.
A Straightforward Guide to Your 1998 Astro PCM Installation
Installing your programmed PCM is a manageable job for a DIYer with basic tools. Following these steps will help ensure a smooth process. The key is to be patient and careful with the electrical connectors.
- Safety First: Always disconnect the negative terminal from your vehicle’s battery and secure it away from the post to prevent any accidental reconnection.
- Locate the PCM: On most of these GM trucks and vans, the PCM is located in the engine compartment, often on the driver’s side inner fender or near the battery. On vans like the Express/Savana, it may be in the LH rear engine compartment.
- Disconnect the Connectors: Carefully unclip and remove the electrical harness connectors from the old PCM. These connectors have locking tabs; do not force them. Inspect the terminals for any corrosion or damage.
- Remove the Old Module: Unbolt the old PCM from its mounting bracket. It’s typically held in place by a few small bolts.
- Install the New Module: Mount your new, pre-programmed PCM onto the bracket and securely fasten the bolts.
- Reconnect Everything: Firmly plug the harness connectors into the new PCM until they click into place. Reconnect the negative battery terminal.
- Perform Security Relearn (If Needed): In some cases, a security relearn procedure may be necessary. This typically involves turning the key to the ‘ON’ position for 10-15 minutes, then ‘OFF’, and repeating two more times. Your vehicle’s service manual will have the exact procedure.
Verified Fitment for Your GM Vehicle
This Electronic Control Module is a direct replacement for service number 09355699 and is interchangeable with part numbers 16266645, 9355699, 16250279, 16258815, 09366810, and 9366810. Please verify your part number and check the list below to ensure compatibility.
BLAZER/JIMMY S-SERIES 98 (RH front engine compartment)
BRAVADA 98 (6-262, 4.3L)
CHEVROLET/GMC 1500/2500/3500 PICKUP 98-99 (Gasoline, LH engine compartment)
ENVOY 98 (RH front engine compartment)
ESCALADE 99 (LH front engine compartment)
EXPRESS/SAVANA 1500/2500/3500 VAN 98-99 (Gasoline)
ISUZU HOMBRE 98 (4.3L)
S10/S15/SONOMA 98 (6-262, 4.3L)
SAFARI (GMC) 98 (LH front by battery)
SUBURBAN 1500/2500 98-99 (Gasoline, LH front engine compartment)
TAHOE/YUKON 98-99 (Gasoline, LH engine compartment)
Frequently Asked Questions
Frequently Asked Questions
Do I need to do anything after I install it?
Because this PCM is pre-programmed to your VIN, it is typically a plug-and-play installation. However, some GM vehicles may require a security relearn procedure, which can be done without special tools. We recommend checking your service manual for specifics.
What information do you need from me?
After you purchase, you MUST provide us with your vehicle’s 17-digit Vehicle Identification Number (VIN). We cannot program and ship the module without it. Please double-check it for accuracy.
Is this a new part?
No, this is a high-quality, tested used part that has been sourced from a professionally salvaged vehicle. This allows us to offer a reliable and affordable solution.
What if my part number is slightly different?
This module replaces several part numbers, including 16266645, 16250279, and others listed above. As long as your vehicle is on the compatibility list and your original part is one of the listed interchanges, this module will work once programmed to your VIN.
Will this fix my transmission problems?
The PCM controls both engine and transmission functions. If your shifting problems are caused by electronic commands from a faulty computer, then yes, this part will resolve those issues. It will not fix internal mechanical failures within the transmission itself.