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4 Easy Steps to Diagnose your Engine Computer (PCM/ECM/ECU Control Module)

Engine Computer, PCM/ECM/ECU Control Module Diagnostics

Today we’re gonna be covering 4 steps to help you diagnose your Engine Computer (PCM/ECM/ECU Control Module) as to whether or not it is the issue in your vehicle. The steps we’re gonna be covering are Visual Inspection, a simple Swap, using a tool such as a Scanner, and Process of Elimination.

1. Visual Inspection

When doing a visual inspection you want to start out by inspecting the PINs. You want to make sure there are all upright and intact. If that checks out, you then want to move on to a smell test – a simple whiff by the plug of the unit will let you know whether the unit is alright. If you get a distinct odor of burnt plastic that lets you know that it’s not ok. At that point, you want to further inspect the board by opening up the unit.

When opening up the unit, you wanna visually inspect for any burnt components or corrosion. If either one of the two is found, the Engine Computer needs to be replaced.

Shop at flagship one inc for engine control module

2. Swap

For Step 2, a simple swap can be done. This will only be effective when working on an older vehicle. Particularly, OBD-I where Engine Computer does not require Programming. At that point, if you can find a Replacement unit matching you exact original Part Number when putting that Replacement into your vehicle, if it can communicate with that Module, that’s a very big hint that the unit is needed to be replaced.

3. Using a Scanner

For step 3 of you diagnostics, you can use a tool such as a scanner. Hooking up a scanner to your OBD-II port will let you know whether or not are there any codes coming from the Engine Computer. Once you have Diagnostics trouble codes, you will be able to know whether the root of the problem was the Engine Computer, or if the Computer is communicating then there’s something else with the vehicle is going on.

4. Process of Elimination

Checking Inputs and Outputs when doing a PCM diagnostics

For step 4 of you diagnosing your Engine Computer, we’re gonna be covering the Process of Elimination. When diagnosing you Engine Computer by process of elimination, we are going to be focusing on two halves: the Inputs vs the Outputs.

The Inputs consist of your Battery, the Ignition Switch, the Fuses, and the Sensors. The Outputs consist of Fuel Injector, the Fuel Pump, the Spark Plugs, and the Starter.

With the Inputs, we have to trace that through to make sure that enough power is getting to the Engine Computer. You start off with the battery – is there enough voltage coming out? Then trace that voltage through the ignition switch, through the fuses, and through the sensors.

If the proper voltage is getting to the Engine Computer then we have to inspect the other half to see if the Computer is doing is the job. You want to confirm whether the Injectors/Fuel Pump is all getting signals, whether you have Spark, and whether or not the Starter is getting a signal.

If you have a proper voltage trace from the battery all the way to the Engine Computer, your Inputs are fine. But if you then go to the other half, and either the injectors, the fuel pump, the spark or the starter are NOT working, that’s gonna let you know that the Computer is receiving enough Power to do its job but something in the middle. within the computer, is not translating, therefore the Engine Computer is not doing its job. At that point, you are able to confirm that the Engine Computer is the trouble. If you do NOT have enough voltage going to the Computer, you go back and further inspect Battery, your wiring to the Ignition Switch, your Fuses, and your Sensors.

If these four steps have not helped you diagnose the Engine Computer properly, at that point you can visit our website or give us a quick call for us to best help you Diagnose your Engine Computer.


For More Information, visit our Website or Call Us Now at 516-766-2223.


The world's top supplier of programmed OEM (Original Equipment Manufacturer) Powertrain Control Modules (PCM), Engine Control Modules (ECM), Injection Control Modules (IDM), Body Control Modules (BCM), Transmission Control Modules (TCM), Engine Control Units and all other car control units. With over a decade in the business, we are the most reliable source when it comes to programming services for replacement engine control modules.

This Post Has 2 Comments

  1. Mark Killingsworth

    Hi, I recently changed my ECM (from another company) in a 2000 Dodge Ram 1500 automatic with a 5.9 gas motor. My truck does not shift now, I am wondering if the replacement ECM was not programmed correctly? or if it was faulty? I am thinking about purchasing a ECM from you, how are they tested to make sure that the unit is not faulty? Or is there a test to know for sure that they are good?
    Thank you.
    PS. It now shows a code po748 with check engine light on.

    1. flagship1inc

      Hello, Please contact our support line directly at 516-766-2223 or connect through our websites live chat and one of our representatives will be happy to answer any questions you have.

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