I heard the familiar rumbles off in the distance. It was summertime in central Florida. I was near the middle of an area that’s called “the lightning belt” — an imaginary line that can be drawn between Tampa and Jacksonville. It’s called this because it is said to have more lightning strikes per year than any other place in the Northern hemisphere. The weatherman said there was a good chance for a thunderstorm that day — and this time it appeared he was correct. The sounds continued to get louder as the storm got closer. Having lived in Florida nearly all of my life, I paid only a little attention as this is an “almost every day” occurrence.
The Pontiac Fiero’s engine had been disassembled earlier in the day and the car was left outside to accommodate the service bay for other work while we waited for the delivery of the parts needed to reassemble it. With the approaching storm’s arrival sure to beat the parts driver’s, I pushed the car inside the bay just enough to where any rain that might blow in wouldn’t cause damage to the exposed components. The wind started picking up and since it was close to the garage door opening, I started protecting the car’s engine compartment with plastic sheeting when…..
I woke up on the garage floor beside the car! I could see the undercarriage as well as the tools on the other side. I couldn’t move. There was a loud ringing in my right ear. I took a deep breath and could smell something had burned, but couldn’t place what it might have been. It wasn’t like plastic or wood, just an unfamiliar smell of something that burned. I felt tingling all along my right side, including the right half of my tongue! Finally, I could move my right arm (was lying on my left side) and in a few minutes was able to sit upright. I gave a quick visual inventory of my extremities; all were intact, then looked around, still quite dazed, but had the wherewithal to know what just happened. I had been struck by lightning!
I’m thankful it wasn’t a direct hit. In fact I’m sure if it had been, I wouldn’t be sharing this with you today. Judging from the damage the strike caused, I’m certain it would have killed me. Every phone wire, phone jack and telephone in the building was destroyed. The TV was no good anymore. The submersible well pump on the property, hanging on over 60 feet of pipe, was destroyed as was the pump at a neighbor’s home some 200 yards away! I have since forgotten what else was affected in that one-second-long event but I’m sure you get the point.
A different kind of lightning
Can you imagine what my initial reaction was when years later I received a call from an owner desperate to get his Ford Lightning running? I had a flashback to that fateful summer day momentarily, but regained my composure quickly enough that it went unnoticed. His truck had stopped running unexpectedly and would not restart. My notes of our initial conversation include, “Owner has a Ford Lightning, the Powertrain Control Module (PCM) has failed (per Ford dealer’s findings). The truck shut off, would not restart and has Passive Anti-Theft System (PATS) Diagnostic Trouble Codes (DTCs). He has another PCM he bought from Ford that needs to be flashed but Ford was unable to perform the task.”
As a mobile technician, I come across all kinds of unusual scenarios that aren’t commonly seen in the stationary repair shops. “The engine quit running while being driven,” the owner said when I arrived at the location to where the dealership had towed the vehicle, and “it has been to a dealership for analysis. The PCM was condemned and must be programmed to the vehicle.” He wasn’t sure why they couldn’t do it, or pretended this very well, and handed me the “new” PCM and the box from where it had been removed.
Without elaborating unnecessarily about all the details, I learned one of the reasons why Ford wasn’t able to complete the repairs on it. There was a “problem” with the Vehicle Identification Number (VIN). I learned the truck’s cab had been replaced, but the original VIN had not been transferred to the replacement. Therefore, the VIN displayed on the door label and viewed through the windshield (1FTRF07263KB98749) really didn’t belong to the rest of the vehicle — so the dealership probably refused to perform any more repairs once this fact was acknowledged by the owner. This VIN is for a 2003 Ford F-150! I was reconsidering the reasons why I chose to be a mobile tech at this point!
During my visual inspection, I also noticed the odometer was displaying only dashes. Performing the vehicle network test using the Ford IDS resulted in eight DTCs stored in the three modules that reported — but showed no communication with the PCM or the IC (Instrument Cluster). I informed the owner that it is impossible to program a module that cannot communicate on the network. I also educated him about how programming a module does not “allow” it to talk on a network (as he had thought). Then I began my own testing.
Where to go?
There are several tests published for when one or more modules are unable to communicate with a scanner. I reviewed them to refresh my memory of procedures that should be followed, and hoped they gave me some insight as to what might make it impossible to access those modules with the scan tool.
In most cases, there are redundant steps to follow, which could waste a lot of time, that if one reads through the whole test before beginning to work on the vehicle, one could skip those and still not misdiagnose the problem. For example, why check the power at the fuses and then again at the module if the fuses are “good?” It would be safe to assume that the fuses are “good” if proper voltage is read at the module if voltage were tested there first. Of course, if the voltage supplied to the module wasn’t what it should be, one could then work towards the battery; look at what voltage was read at the fuse, at the battery connections to the fuse block, at the ignition switch, etc.
I thought now would be a good time to take a quick look at the communication networks and the PCM wiring diagrams. If you’re reliant on one service information provider, then you might get a bit frustrated if you are the one trying to look for the correct network communication wiring diagram for this truck. I have a few providers, precisely for when I run into information that doesn’t match the vehicle I’m working on. That’s exactly what happened when I went to use my first choice.
It’s instinctive to just look for a “Pickup” or “F-150,”, since “Lightning” wasn’t one of the choices available at the time I was entering the vehicle information. I saw two choices for a 2004 Ford, but the “Pickup F-150” choice showed me an incorrect diagram (and I went back thinking I erred when building the vehicle). The second time I made the other choice, “Pickup Heritage F-150.” What would you have done if your information provider’s data is incorrect? What would you do if neither choice matched the vehicle? Add the complication of possibly having the wrong wiring in the vehicle because the truck cab was replaced and now you’ve got a REAL mess!
I chose an alternate source of service information, the OEM’s site to compare with my aftermarket information. Ford’s Professional Technician Society (PTS) site, also known as Ford’s Installer Support, showed the same wiring diagrams as Mitchell’s (Shopkey). I knew my choice was correct when I saw “Heritage F-150” is what Ford’s service information indicated this vehicle is — after I identified it by the VIN on their website. It would have saved me time to look there first in this case.
Once I had accurate-for-the-vehicle service information, I was able to perform circuit testing. It is nearly impossible to do so without an accurate wiring diagram! The easiest test to perform verified the integrity of the Standard Corporate Protocol (SCP) network wiring by using continuity. Continuity to both SCP wires was verified between the PCM connector and the Data Link Connector (DLC) under the dash by back-probing both while the ignition key was off. Neither wire was shorted to the other, nor was either shorted to voltage or to ground, and both showed continuity between the connectors. This meant the communication network to the PCM was intact.
My next test was to verify the integrity of the PCM’s grounds. With the connector removed from the module, I applied battery voltage to the three ground terminals through a back-probe attached to each wire, one at a time. I used a Power Probe 3 only because it was already attached to the battery. The method I used caused the circuit breaker to “trip” in my tool, which indicated the circuits were able to withstand a substantial load, and didn’t display any voltage drop conditions.
It is a quick, easy and conclusive test for ground circuit integrity. Be aware, one must exercise extreme caution when performing tests this way! Please make sure, before you push the switch on your tool, that there are absolutely no electrical devices attached to the circuit or between the output of your tool and the battery (or batteries). If you aren’t sure, then do NOT apply voltage to the circuit to which you are attached! In fact, I recommend people install safety devices to their tools to prevent the accidental introduction of battery voltage into a circuit being tested.
Grounds good, on to power
After verifying the grounds were good, I needed to measure the battery-supplied and ignition switch-supplied voltages at the PCM connector. I reconnected the PCM electrically and tested for adequate voltage by back-probing the appropriate terminals. It was during this test when less than 8 Volts DC was measured on the “VPWR” circuit, #361 (PCM Pins 71 & 97). Suspecting the possibility that the dealership technician condemned the PCM because an internal fault was causing such a voltage drop on these circuits, I disconnected it and measured the voltage again. It was identical!
This meant the voltage supply from the ignition switch was insufficient. A look again at the wiring diagrams showed these two circuits were supplied voltage by just one fuse. I removed the Battery Junction Box (underhood fuse block) cover. A visual inspection of the fuse in the circuit revealed a yellow colored wire was forced into one socket that the fuse’s “leg” was meant for, in addition to the fuse! My Power Probe volt meter indicated a “good” supply on one leg yet only 8 VDC on the other.
Even after removing the non-factory-installed additional component (yellow wire) from where it was forcibly inserted, the voltage readings didn’t change! The fuse was damaged; the loop between the two fuse “legs” was barely touching one of the “legs!” Whether it broke from being wedged into place or due to vibration, the fuse was producing a voltage drop — so much so the PCM wasn’t getting enough to “wake up” when the key was turned on. I replaced fuse #18 and found the odometer was now properly displaying numbers instead of all “dashes.” I was now able to communicate with both the IC and the PCM.
I successfully performed all PCM self-tests and cleared all CMDTCs throughout the vehicle, verifying the PCM wasn’t faulty. At the owner’s request I installed and programmed the replacement PCM (since he said it wasn’t returnable anyway). I called this job done.
There are times when I see guidelines or advice printed by a manufacturer about a purchasing choice, which warns of inferior products that may adversely affect the operation or longevity of something the manufacturer produces. For instance, we all (should) know not to use inferior oils in an engine designed for use with a specific product. Doing so may cause problems that could be catastrophic.
Another example, certainly one by now we are all aware of, is the GM service alert (#07-08-45-002) where “concerns” were published about how well certain aftermarket blade-type fuses performed in certain applications. The TSB described in detail why GM was concerned and placed emphasis on why, in the name of safety mostly, shops and dealerships should inspect their inventories for faulty items and immediately remove them so no technician would install them in a customer’s vehicle. I don’t know if the fuse producing the voltage drop was one GM mentioned or not.
There are also times when I see guidelines or advice distributed by experts in their field(s). I heed the warnings of weather experts now when they warn of severe thunderstorms approaching — ever since that fateful summer day when a lightning strike nearly took my life. The only lightning I’ll mess with now is made by Ford!
P.S. - Can a voltage drop test be done with a test light? Think about that when you’re checking fuses from now on!
