How to Check Your Engine Control Computer for Problems

An engine control computer is the brain of your engine, more or less. It gets info from sensors and then tells your engine what to do based on the memory banks. It creates computations for the memory banks to use, to tell the engine how to react. Examples of some of the jobs it does are: fuel delivery, emissions systems and your timing.

Your vehicle should have a wiring configuration or diagram in the owners manual, and you will need this to proceed. You should look to see what parts look different, or if something is just not working correctly, always check the power. When a few areas aren't working right, you can check that specific circuit to make sure they are working correctly.

You ECC normally has a diagnostic capability in the memory banks. Small problems like bad wire connections can cause your computer to try to fix itself, and then overcompensate by making changes in your entire system. Then you would think it was a separate component and not the computer.

Any time you are diagnosing a computer, you can't overlook basics and just begin replacing everything. Try to look at the rest of the vehicle, to make sure there are no problems that could be causing a computer error. Some people try to clean the engine, and this is fine. But do not use steam, as any temperature over 300 degrees Fahrenheit will cause corrosion in the computer, and it will never work again.

Bad connections are the most common problem with computers. Check for damaged or missing connections, and connector pins that are bent or broken. If yours has pins, remember to feel, as they should fit tightly around a small paperclip. Check your power source as well as all connections going to the power source, including your ground. You normally have 2, sometimes 3 power leads. One will always have power, so that even when your car is turned off, your ECC's memory banks keep information. The second in most cases, and always if you have a third, only gives power when your car is turned on. You have fuse links to protect these wires, so check the fuses for these. These wires are always near your battery or starter, even the starter relay on some cars.

Your ground numbers will vary, but all power grounds are for motors and solenoids, while the sensor grounds are used for going to the computer and then a ground source. Check ground straps and wires on the engine, and make sure the eyelet of the ground wire at the cylinder head is tight and not rusted or painted. After checking all wires for damage, just make sure they are all plugged in or attached. If there are bare wires, don't worry. If they are running to the distributor, they are shielding wires. These connect to a ground and then absorb your radio frequencies that may cause problems determining RPMs to the computer. As long as all of these things are present and not damaged, you will need to replace your computer.