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Pay attention to details when swapping an engine or transmission

Wednesday, November 1, 2017 - 07:00
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I was called to a shop for a simple task of reprogramming a new ECM on a 2012 Ford Focus with a 2.0L engine (Figure 1). There are a lot of shops in the industry that do not want the responsibility of programming a new ECM due to the liability and costs involved in doing the job. Some shops may not be properly equipped with the proper interface or laptop and may not want to go out to the Internet to fill out an application to sign up with an individual manufacturer and purchase a daily subscription. This may be coupled with a need to be registered through NASTF as a Security Professional to access theft procedures that may be needed during the post programming procedures. There is also the need to have a proper battery charger in the shop that can provide a "Programming" mode that will maintain a specific voltage range while a current surge occurs such a cooling fan coming on during the programming process. Some manufacturers will terminate programming if voltage falls below 13.1 volts or if voltage exceeds 14.0 volts. An older battery charger with only Low, Medium and High settings is not recommended and may pose a problem if too much AC ripple is introduced.

Figure 1

Is the ECM to blame?
When I arrived at the repair shop I proceeded to question the shop technician to see why he had made the decision to replace the ECM. It is not uncommon for a shop to jump the gun to condemn a control module without probable cause. I'm not in the business to just go ahead and reprogram a Control module at will without making sure it will resolve their issue with the vehicle. The last thing I need is to charge a shop to program a new or used control module only to find out that it was wasted revenue without a cure for their problem. I will usually question the shop to see if they followed the proper procedures to condemn the module. This would include checking power and ground feeds, shorted reference voltages, communication lines or even an issue with their testing equipment.

Figure 2

The shop told me that they just replaced the transmission (Figure 2) and when they got done the vehicle would no longer start. They checked the vehicle and found that the ECM was not responsive so they figured it might have been damaged during the repair procedure. This is a bad situation of "Drive them in / Push them out". We have all been there before at one time or another in the repair business. It becomes an unwanted marriage between you and the vehicle and your only way out is to resolve the issue at your own cost because you can't expect the customer to pay it. In the end it all becomes a learning experience but you’re under the gun to get things resolved ASAP before the customer is aware of his or her new dilemma.

When I hooked up to the new ECM to program it I was unable to communicate with it. The shop was under the impression that the new ECM would not communicate because it needed to be programmed. This is misinformation that I see a lot of shops seem to believe in and I had to school them on this belief and to educate them on how to evaluate no communication issues with a vehicle. They have to always make sure that prior to condemning a controller they check EVERY power and ground feed at the ECM and scan the entire vehicle to make sure it is not just a single control module issue without focusing too much of their attention only on one single controller. By scanning the entire vehicle they will get a better evaluation of all the operating systems that are responsible in starting the vehicle. Sometimes the clues to their problems may be resonated in other modules on board that may put them on a better path in their diagnostic process.

Start at the beginning
I placed my scan tool on the vehicle and did a full scan of the entire vehicle. I discovered that only five control modules were present on the multiple networks this vehicle had on board (Figure 3). These were the Audio, Body, GPS, Instrument and Tire Pressure Monitor control modules. This vehicle had three separate CAN networks on board: Medium Speed, High Speed and Entertainment CAN networks. The High Speed CAN network was inoperative. The controllers on this network included the Transmission, Engine, ABS, Power Steering, Steering Angle, Air Bag and Occupant Classification control modules. It was highly unlikely that all these control modules were bad or that they all had a common power or ground feed failure. What was common to all of them was a network circuit that was either open or shorted.

Figure 3
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