Diagnosing a Brain Dead Ford Ranger

Michael from Clinton Mobile Technician Posted   Latest  
Case Study
2008 Ford Ranger 2.3L (D) 5-spd
No Crank / No Start
Security Theft / No Start

On Friday I was asked to program a replacement PCM on a 2008 Ford Ranger. The vehicle had been diagnosed at the dealer as a bad PCM. It was a no-start with the PATS (immobilizer) lamp flashing. The instrument cluster had hyphens all the way across the odometer. When I attempted to program the PCM, there was no communication. I switched to read codes and found codes listed for no communication between the Instrument Cluster and several other modules including the PCM. I was unable to spend time on it so I scheduled time on Saturday to check it out.

Forward to Saturday AM. After verifying the same communication issues with the original and the replacement PCM, I decided to do some troubleshooting. I first disconnected the battery and checked the integrity of the CAN network. It had 117.8 Ohms. Something was missing here. From the block diagram I could see that the Instrument Cluster and the PCM each had the terminating resistor for opposite ends of the network. Since it was simple to disconnect the PCM, I started there. The network stayed steady at 117.8 Ohms. So the Problem appeared to be in the wiring between the PCM and the DLC. Next test was reading continuity between the terminals at the PCM and the DLC. Wires came in on pins 11 and 23 on the center connector. What? There was continuity. What is going on here. I looked at and worked with the connectors that plug into the PCM. The network ran through the center connector. I examined the pins at the PCM. I did not have my drag test pins so I was not able to test the barrel end. In working with the connectors I noticed that the detents that hold the release bars were all worn or broken. The connectors moved out slightly after pushing them in place. I surmised that when the last PCM was installed the detents were broken. After time, the connectors walked out enough to loose the network connection. After getting the connectors to stay in place I read the CAN resistance again. 60.3 Ohms. Hopped in the truck, turned the key and it started. The mileage read correctly. No more codes.

The best practice for repairing this is to replace the connectors or the entire loom. This was not an option I could sell. So what I did was use some Q-Bond to hold the bars in place. If needed it could be chipped off to access the PCM but it would hold the bars in place. Again we see that having the techs follow a flow chart or them using the trouble code as a diagnosis is not the best practice. The end user went to the dealer for top notch diagnostics and was led down the wrong path. In one hour the problem was found and corrected without selling any parts. This was done successfully.


Mario from Weston



Nice work! It's always nice to diagnose a network issue with an ohmmeter


Geoff from Lahaina



Glad you found it! I had an old POS "suped-up" S-10 in here one time, and the trick to the no-start was pulling sideways on one of the PCM connectors (to tweak the circuit board). We cobbled something together to hold it cocked, and told them they needed a PCM. They are still driving it cobbled (of course).


Martin from Burnaby



Good work on the diagnosis and fix Michael. The one thing that sticks out though, is the frequency in which shops or individuals make unsubstantiated statements that a problem was diagnosed or miss-diagnosed "at the dealer". As both an independent shop technician, followed by many years as a dealership technician, I've seen these claims errantly made in both camps. Some dealerships will make similar claims that the hack was done "at the aftermarket" shop.

At the dealership, a vehicle would often arrive "broken" after being "back yarded" by the customer or his "hack mechanic buddy", with connectors broken and more. I've literally had vehicles brought to me with large broken chunks in boxes in the trunk, to reassemble and repair. I've worked on vehicles that had been misdiagnosed wherever and the only focus for me was/is what I am faced with repairing at this minute. What "he or she did elsewhere" doesn't factor into my diagnostics.

Of course, customers not wanting to spend money on diagnostic time is common, so when a visual identification of what clearly is a major contender and contributor to a concern is made after a just a few minutes, an estimate for a complete diagnosis with accompanying parts may be in order, to be presented to the customer as a worst case cost. Typically, an RO will read, "Check and report"....... That means preliminary inspection to form an idea of what diagnosis and costs might be involved to effect a professional repair.

Now, in the scenario you described above, it appears that "Mr. Pryrdriver" had already worked his/her magic on the connectors. So, perhaps the PCM connectors were a little misshapen, the retention latches broken, terminal positive assurance and connector positive assurance pieces damaged beyond any useful function. Perhaps the damage that you experienced was actually and just as likely to have been caused by the very shop that hired you to program the vehicle!

Said customer knowing that a repair such as the one you have just completed could have required a PCM and some wiring connector repair/harness replacement at worst case scenario, chose to abort the diagnostic process and take his vehicle elsewhere and you were hired for the final stage of the fix at the shop that he chose. You then located the root cause of the problem, believing or being led to believe that it was done at the dealership and subsequently managed to effect what you feel will be a reliable repair, by less costly means.

This same scenario plays out almost daily in both directions with indy claiming dealer and dealer claiming indy to be at fault or a "hack", when increasingly often the hack was done by the customer and/or his buddy.

So, to remain professional, unless one saw and experienced for themselves, the hacked diagnosis and repair first hand, I strongly recommend leaving all hearsay descriptions out of any discussions. Customers will often lie or provide false information, believing that it will save them money and blaming another technician or shop without actual proof, simply lacks professionalism.

The simple fact that surrounds your diagnosis is that there was some evidence of connector TPA or CPA damage, that could require a harness, or might possibly be repairable by other means to ensure terminal retention. Now, if your creative retention method fails sometime in the future and the vehicle ends up at a capable dealership or independent shop, the customer will claim ignorance except that the last shop (you) caused the problem and so the story goes on!

As far as hacks in the profession, they abound in both independent and dealerships, since the source for either technicians when hiring is also from both arenas. Dealerships not growing their own, often hire whatever "warm body" crosses the threshold and likewise, some who are unable or unsuited to the work leave the dealership environment and seek greener pastures in independent shops. In reality, these technicians are often transient, leaving a trail of devastation and comeback repairs necessary for those of us who have to deal with the aftermath of their lack of diagnostic and repair skills, for the next six months or so.

I am sure that some of you who are mobile techs cringe at the thought of going to some shops, because of trends that you see on every visit that indicate damage was caused at the not shop, not elsewhere! I was mobile in 1979 and experienced this scenario first hand.

So, in the situation that you described, I would simply have mentioned that "A previous unsuccessful repair elsewhere, had left some visible component damage, that was determined to be the root cause of the current concern."


Michael from Clinton


Mobile Technician

Hi Martin, 

Thank you for your constructive criticism. It is good to see other perspectives and learn from them. The owner of this vehicle had purchased it from a private party. In looking at the PCM, it has fairly fresh Silver paint on it. A replacement had been done previous to the sale. They had no idea of any earlier repair. The shop that replaced the PCM did not recognize the issue with the connectors either. So there is that.

My concern is that a blanket statement was made to the owner that he needed a new PCM. "A previous unsuccessful repair elsewhere" would be a more fair statement indeed. I suppose it is my own bias. I hear from car owners all the time that they are going to the dealer because they are the only ones that can do it correctly. As you stated, the dealers pull from the same pool of technicians as the independents. All technicians including myself make mistakes in diagnosis. The dealer is not the ultimate in automotive repair. They do have the advantage of all the factory tools and repair information. The do see all the pattern failures first. In the end it is about the education and effort put forth by the technician working on the problem.


Martin from Burnaby



No worries Michael. We are all here to serve together and hopefully raise the bar to a level where truly professional technicians receive the respect and remuneration that they are worth. I worked with some of the best and some of the worst, in my first 12 years as an independent and in the following 23 years as a dealership technician. Unfortunately hacks abound everywhere, despite the availability of and even participation in training.

As for having all of the factory tools, if only it were true! VBG. In the perfect world that may be so, but dealership technicians will often relate how they have had tools stolen by former employees and the company had not replaced them, or a tech here or there keeps a tool hidden away for their own personal use. As for the "pattern" failures, for sure there are some but those are relatively few and far between in the big scheme of daily events in dealerships. Sure, the intake gaskets leak on this or that may fail, but many more challenging electrical diagnostics and other issues are often not related to pattern failures.

Just as with many independent repair facilities, most dealerships are owned by independent business people. As such, operating protocols and the business acumen at one location is almost a polar opposite to the next franchised dealership. So, while there may be quality issues at one dealership or another and the same situation within independent facilities, the common denominator for quality diagnosis and repairs still appears to fall on the technicians' shoulders.

If we as a group here, can have a positive influence on those who become members, who may be struggling or stuck in a rut and assist those souls to elevate their skill sets and find employers who value employees instead of viewing them as a CODB, it is one small step forward!