Short answer: the engine computer (called the ECM, PCM or ECU depending on the maker) is not in one standard place. On most trucks it sits under the hood near the firewall or next to the battery; on many cars it sits inside the cabin behind the glove box or under the dash. Below are locations we could confirm from the makers' own documents or from owners who found the module themselves, how to read the part number on its label, and what to check before you replace it.
"Where is the ECM on my Silverado?", "where is the PCM on a Ram 1500?" and "where is the ECU on my Accord?" are some of the most common questions about engine computers. Generic answers like "under the hood or under the dash" don't help when you are standing at the truck with a wrench, so this guide names the vehicle and says where each answer comes from.
ECM, PCM or ECU: same box, different names
The makers use different names for the engine computer. GM's service manuals call it the engine control module (ECM). Ford's parts list calls it the powertrain control module (PCM), basic part number 12A650, and Chrysler's recall documents also call it the PCM. Toyota calls it the ECM, and Honda writes ECM/PCM. If you are looking for the computer that runs the engine, all of these names point to the same box.
How to read this guide
- Maker's document: the location is stated or pictured in the maker's own manual, recall or bulletin.
- Owners confirm: owners on that vehicle's forum found the module there, and other owners or the person asking confirmed it. We name the model year the owners had.
- Owner report: one experienced owner or moderator answered, without a second confirmation.
We left out vehicles where we only found one unconfirmed post or answers that disagree. Locations can change within a generation, so check your own vehicle before you unbolt anything.
Chevrolet Silverado and GMC Sierra
- 2015 Silverado and Sierra (maker's document): GM's 2015 Silverado/Sierra electrical manual places the engine control module in the engine compartment, at the left front of the engine, near the underhood fuse block. GM's 2015 Tahoe, Suburban and Yukon manual places it in the engine compartment, to the left of the engine.
- 2007 Silverado and Sierra, the 2007-2013 body style (owners confirm): on the driver's side under the hood, next to the extra battery tray toward the fender. Owners point out that two modules sit there together: the engine computer is the larger one, and the other is the transmission module.
- 2000 Silverado, the 1999-2006 body style (owners confirm): under the hood above the steering box, under a black plastic cover. The owner who asked found it there.
Ford F-150
- 2004 F-150 (owners confirm): under the hood on the upper firewall, on the passenger side. The owner who asked found it there.
- 1997 F-150 (owners confirm): inside the cab, behind the passenger kick panel, and removal starts from the engine compartment. The owner who asked found it, partly hidden by the battery. Owners note a sticker on the module with a short code, three letters and a number (for example IMP4), that identifies the model.
Ram, Dodge and Jeep
- 2018 Ram 1500 (maker's document): Chrysler's recall U87 instructions show the PCM location in a photo labeled with the air filter housing and the PCM connectors, so look next to the air filter housing.
- 2018 Dodge Durango and 2018 Jeep Grand Cherokee (maker's document): the same recall has the technician remove the coolant reservoir fasteners to reach the PCM connectors, and the PCM comes off a mounting bracket on the power distribution center (the underhood fuse box). A ground strap is attached at the PCM.
- 1997 Ram 1500 (owner report): on the right (passenger) side of the firewall. Follow the large wiring loom near the cowl; the PCM has three plugs.
Toyota, Honda and Nissan
- 2005-2008 Toyota Corolla and Corolla Matrix, 1ZZ-FE, 2WD (maker's document): Toyota's recall procedure tells the technician to locate the ECM under the glove box compartment.
- 2001 Honda Civic DX and LX (maker's document): Honda's service bulletin reaches the ECM/PCM by removing the passenger's side lower dashboard cover and kick panel, then the glove box.
- 2002 Nissan Altima (owners confirm): behind the glove box, to the right of the blower motor; drop the glove box to reach it. One owner suggested under the steering column, but the others agreed on the glove box.
- 2011 Honda Accord (owner report with photos): under the hood, next to the battery, according to a forum moderator who posted photos of the location and the removal.
How to find the part number on the label
Once you find the module, the label is what you order by. The makers' own documents show what to look for:
- Chrysler, Dodge, Jeep: Chrysler's bulletin 18-042-14 says the part number can be taken from the label on the old controller. On a 1997 Ram, an owner found the number in the middle of the label, starting with P.
- Ford: Ford's basic part number for the PCM is 12A650; the full number on your module's label carries a prefix and suffix around it (for example 7T4A-12A650-GE on a 2007 Edge), and Ford's own bulletin says the exact number needs a catalog lookup.
- Toyota: Toyota's recall procedure has the technician read the ECM part number on the unit (Toyota ECM numbers start with 89661) to decide what to do.
- GM: use the number printed on the module's label together with your VIN.
Give the full number from the label and your VIN when you order. The same vehicle can use more than one computer depending on engine, transmission and options.
Before you replace it: what the makers say to check
- Connectors and water: GM's bulletin 08-07-30-021H for 2007-2013 Silverado and Sierra and related trucks lists corrosion and water intrusion in control module connectors among the causes of communication faults and no-crank, and tells technicians not to replace any control module until the cause has been isolated.
- Water in the headlamps (2016-2018 Silverado and Sierra 1500): GM's bulletin PIT5546E says water in a headlamp assembly or its connector can cause a no-crank, a dead battery, or the ECM failing to program. Inspect the headlamps first.
- Ignition coils: GM's bulletin PIP5038B for 2009 Acadia, Enclave, Traverse and Outlook 3.6L warns that a damaged ignition coil can damage a new ECM, and says not to start the engine until the coils are checked. Ford's bulletin 12-8-17 replaces the coils together with the PCM on affected 2007-2008 Edge and MKX models; see our Ford Edge and Lincoln MKX PCM guide.
- Battery and ground strap: Chrysler's recall U87 starts by disconnecting the negative battery cable, and reinstalls the ground strap with the PCM.
After you replace it
A replacement computer has to be set up for your vehicle. Chrysler's recall U87 says the new PCM is programmed with the vehicle's original VIN and mileage, or a trouble code may set. Honda's bulletin 00-098 says a new ECM/PCM must be programmed to accept the immobilizer's key codes or the engine will not start. What your vehicle still needs after install depends on the unit you buy; our listings say whether a unit is Plug & Play or programmed to your VIN.
Frequently asked questions
Where is the ECM on a Chevy Silverado?
On the 2015 Silverado and Sierra, GM's manual puts it at the left front of the engine near the underhood fuse block. Owners of 2007 trucks find it on the driver's side next to the extra battery tray, and an owner of a 2000 truck found it above the steering box under a plastic cover.
Where is the PCM on a Ram 1500?
On the 2018 Ram 1500, Chrysler's recall U87 shows it next to the air filter housing. On a 1997 Ram 1500, an owner found it on the passenger side of the firewall with three plugs.
Is the ECM under the hood or inside the car?
It depends on the vehicle. The trucks above have it under the hood; the 2005-2008 Corolla, 2001 Civic and 2002 Altima above have it behind or under the glove box.
Is the ECM the same as the PCM and the ECU?
For finding and replacing the engine computer, yes: the makers use different names for the same module. Some vehicles also have a separate transmission module mounted nearby, so read the label before you unplug anything.
Do I need to disconnect the battery to remove the ECM?
Chrysler's recall U87 procedure starts by disconnecting the negative battery cable, and that is the safe way to start on any vehicle.
Engine computers from NPC Automotive Computers
Every NPC unit is remanufactured and programmed before it ships, and it comes with a lifetime warranty. Order with your VIN and the part number from the label on your old computer. Each listing says whether the unit is Plug & Play, with no dealer or locksmith visit needed after install, or programmed to your VIN, in which case plan for the key or theft-deterrent relearn at a dealer, a shop with the maker's tools, or a locksmith. Not sure which unit fits? Call us before you order and we'll check it with you.
