AES Modules ECM Troubleshooting

AES Modules

Notes to Licensed Installers

ECM Troubleshooting

AN ECM is simply a computer that operates in a network in your vehicle. ECM’s only function correctly when they are integrated into your vehicle’s network security and operating system. As a result there are many problems associated with ECM repair and replacement that can only be seen or diagnosed with the ECM installed in your vehicle’s network and using an OEM specific scan tool.

If you are not experienced in ECM replacement, specific to the vehicle you are working on, do not attempt to work on the vehicle network.  Typically an experienced Master Tech, with an OEM specific scan tool is required.  This is why the AES Modules warranty is only valid if a licensed shop installs the ECM. It is also why AES Modules offers Master Tech assistance through our Tech Assist program.

Typical ECM replacement questions:

Q. Before I put in a new ECM, how do I know that it will fix my problem?
A. Before installing an ECM, you must test ALL related circuits on the vehicle to determine which one(s) caused the failure. Use a DVOM and measure the resistance at the harness connector. If any values are less than the specified ohms, you must find and fix the cause.


Q. I plugged in the new ECM and it didn’t fix the problem. What now?
A. Prior to replacing the ECM, the installer should determine what caused the ECM to fail. Common areas that cause failures are: poor grounds and powers, bad wiring, shorted solenoids/relays, or misdiagnosis.

Q. The replacement ECM for won’t start the vehicle. Why?                                                                                                                        
A. Your installed module may be in theft mode and/or need on-board theft learn or programming performed to allow the vehicle to start.

Q. I replaced the ECM and now I have a steady check engine light and a different code than I had before. Why?
A. Your previous, broken, ECM may not have had the functionality required perform vehicle diagnostic checks that would set a code and turn on a check engine light. The replacement ECM has restored this functionality. You must scan codes and perform diagnostic test for the code set before condemning the replacement ECM.

B.  Programming may need to be done specific to your vehicle if a code is setting for a component your vehicle does not have.

Q. I put my new ECM and PROM in and the PROM blew out. Why?
A. The most common cause of PROM burn-out is when the PROM is put in backwards. This will short out the PROM. It is very important that the PROM be inserted in the ECM properly to avoid this problem.

Q. I replaced the ECM and now I have a steady check engine light and a code 51. Why?
A. Make sure The PROM is fully seated. Also check for bent or broken prongs on the PROM.


  • Find out what damaged the original Module. Fix      whatever caused the damage before installing replacement unit.
  • You are urged to refer to a suitable service manual before attempting to make repairs. If you do not have such a manual, or lack the experience, you should seek the services of an experienced technician, specific to the vehicle’s manufacturer.


  • A Module usually does not fail unless something has put an excessive electrical load on the unit. Resistance, Voltage and Ground checks must be performed on each circuit controlled by or connected to the Module, test all solenoids, injectors, coils, and relays for shorts or defects. Any faults or defects must be corrected before installing the replacement/repaired unit or the WARRANTY WILL BE VOID.


  • Additional specific diagnostic information may be supplied with this replacement unit. Be sure to perform all checks and tests before proceeding with the installation.


  • Do not remove the Module from its shipping carton until you are ready to install the unit.


  • When handling the Module, use extreme care to avoid damage from static electricity.


  • Do not allow dirt or fluids to contaminate the Module electrical harness connections.


  • Some Modules have components or special hardware that must be reused. Be sure to note how components attach to the original unit.


  • Some Modules will require Programming, Configurations, Coding, Initialization, and/or theft system re-learn with specialized diagnostic equipment AFTER installation for the module operate as designed.


  • This Module is guaranteed to fit and function in the application for which it is listed. Carefully verify the replacement unit number to be sure the unit is correct and all set procedures complete for your application.


Removing ECM

  1. Disconnect the battery ground terminal to      avoid risk to damage to electronic components. Power must never be      on during installation or when servicing the replacement ECM.
  2. Locate and remove the ECM. If necessary, refer      to the vehicle service manual for ECM location and proper disassembly      procedures. Be sure to save all mounting hardware and assemblies and note      how each harness connector attaches to the original ECM.
  3. For units located in the engine compartment,      the area around the ECM connectors must be kept clean to protect the      replacement unit.

Electronic components can be damaged by static electricity that builds up on parts, tools, clothing and your body. The following precautions will reduce the risk of damage from these sources.
DO NOT TOUCH the electrical terminals on the parts.
BEFORE OPENING the package and handling the unit, use a grounding wrist strap or anti-static mat to protect the electronic module from static electricity damage. If not available, touch a known good ground frequently while handling the unit. Failure to do so will damage the unit and VOID THE WARRANTY.


Installing ECM

  1. Installation is the reverse of the removal      procedure. Follow any additional enclosed instructions or labels on the      replacement ECM. Be sure to transfer all parts and components from the      original unit to the replacement unit.
  2. Recheck all connections, then reconnect the      battery ground cable.
  1. 3.      Before running system diagnostics, check the electrical harness for disconnected, frayed or worn wires. Also, be sure to check for loose, bent, broken, improperly seated terminal connections or corroded terminals. Correct any problems before continuing the troubleshooting procedure.

Testing vehicle with replacement ECM

  1. Before testing the ECM and operating the vehicle, make sure all diagnostic tests and procedures have been performed and any defective components have been repaired or replaced.
  2. After verifying that all systems function properly and that there are no error codes, road test the vehicle.