PATS & Fuel problem Troubleshooting help needed
Fleet Mechanic
Joined: Jul 2010
Posts: 1,753
Likes: 34
From: Los Angeles, Ca.
Update on Excursions and Tachometer bounce.
Today when mine died and wouldn't start I noticed that I had no tach bounce so I started suspecting the CPS. Fired up the Torque Pro app and I had injection showing when cranking so I figured it was the low fuel level, and it was. I don't know if it's every Excursion or just mine, but the tach had no movement while cranking.
This also means that I might have been wrong about PATS killing tach bounce, MINE had no bounce when my PATS was in theft mode but it turns out that it doesn't when not in theft mode too. Sorry.
Today when mine died and wouldn't start I noticed that I had no tach bounce so I started suspecting the CPS. Fired up the Torque Pro app and I had injection showing when cranking so I figured it was the low fuel level, and it was. I don't know if it's every Excursion or just mine, but the tach had no movement while cranking.
This also means that I might have been wrong about PATS killing tach bounce, MINE had no bounce when my PATS was in theft mode but it turns out that it doesn't when not in theft mode too. Sorry.
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Stewart
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Fleet Mechanic
Joined: Nov 2015
Posts: 1,838
Likes: 187
From: NoVA
Just wanted to post an update that after all the various troubleshooting steps, my truck went into the dealership yesterday. Today, they came back with a diagnosis of a dead PCM. I need this for my 2003 7.3 EX.
Original#2C3Z-12A650-AF
Updated#2U7Z-12A650-HPA
Found them in stock at Flagship One Auto for $1499 :O On the fence whether to send mine to be fixed and try. Or, suck it up and order a $1500 part that may/may not fix the problem
Anyone here have any dealings / reviews of prior purchase from this vendor?
https://www.fs1inc.com/2u7a-12a650-h...d-dpc-492.html
Original#2C3Z-12A650-AF
Updated#2U7Z-12A650-HPA
Found them in stock at Flagship One Auto for $1499 :O On the fence whether to send mine to be fixed and try. Or, suck it up and order a $1500 part that may/may not fix the problem
Anyone here have any dealings / reviews of prior purchase from this vendor? https://www.fs1inc.com/2u7a-12a650-h...d-dpc-492.html
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Fleet Mechanic
Joined: Nov 2015
Posts: 1,838
Likes: 187
From: NoVA
Forgot to update for a while.
Sent the PCM to Diesel Technology of Chattanooga to diagnose issues with the PCM. Here's the update...
o
So, the PCM is back with the shop to continue the work. Hope to hear from them soon.
Sent the PCM to Diesel Technology of Chattanooga to diagnose issues with the PCM. Here's the update...
Prakash,
I got your PCM in today and just finished testing it.
By all my tests, there is nothing wrong with it except that the terminals where the chip plugs in are very tarnished, so if you had a chip in it when these problems started that could account for a lot. (However, you told me it came with a programmer installed and you removed it, and made no mention of a chip, so I'm guessing you do not have a chip.)
My test bench is basically a complete 7.3 wiring harness minus the truck: PCM, IDM with 8 injectors connected to it, Glow Plug Relay and Glow Plug Control Module, Intake Air Heater Relay, Wastegate Solenoid, Air Bag Module, Fuel Pump Relay, Trans Range Selector & Trans Solenoids, etc, with a microprocessor that generates a cam position sensor so the PCM thinks its in a running engine. I have the OBDII port to connect a scan tool to, potentiometers to simulate all the engine sensors (ICP, EOT, etc) and a breakout box for the oscilloscope. So, if it runs on my test bench, it darn sure should run on a truck.
My scan tool connected just fine, and all the data from engine sensors and controls was fine.
My first guess as to what is wrong is that the Exhaust Back Pressure Sensor is shorted out, killing the 5 Volt reference, which is shared with the PCM's internal operations (microprocessor, EEPROM, etc).
Second guess is that the ICP sensor is shorted, causing the same problem.
Third guess is blown fuses. Replace the fuses that power the PCM, even if they look and test good. I've see multiple instances of fuses looking & testing good with an Ohm meter or test light, but not passing enough current to supply a load.
Fourth guess is some severe melting/burning of the engine wiring harness.
If you use, or plan to use a chip in the future, the contacts on the PCM where the chip plugs in need to be re-soldered to prevent them tarnishing.
I got your PCM in today and just finished testing it.
By all my tests, there is nothing wrong with it except that the terminals where the chip plugs in are very tarnished, so if you had a chip in it when these problems started that could account for a lot. (However, you told me it came with a programmer installed and you removed it, and made no mention of a chip, so I'm guessing you do not have a chip.)
My test bench is basically a complete 7.3 wiring harness minus the truck: PCM, IDM with 8 injectors connected to it, Glow Plug Relay and Glow Plug Control Module, Intake Air Heater Relay, Wastegate Solenoid, Air Bag Module, Fuel Pump Relay, Trans Range Selector & Trans Solenoids, etc, with a microprocessor that generates a cam position sensor so the PCM thinks its in a running engine. I have the OBDII port to connect a scan tool to, potentiometers to simulate all the engine sensors (ICP, EOT, etc) and a breakout box for the oscilloscope. So, if it runs on my test bench, it darn sure should run on a truck.
My scan tool connected just fine, and all the data from engine sensors and controls was fine.
My first guess as to what is wrong is that the Exhaust Back Pressure Sensor is shorted out, killing the 5 Volt reference, which is shared with the PCM's internal operations (microprocessor, EEPROM, etc).
Second guess is that the ICP sensor is shorted, causing the same problem.
Third guess is blown fuses. Replace the fuses that power the PCM, even if they look and test good. I've see multiple instances of fuses looking & testing good with an Ohm meter or test light, but not passing enough current to supply a load.
Fourth guess is some severe melting/burning of the engine wiring harness.
If you use, or plan to use a chip in the future, the contacts on the PCM where the chip plugs in need to be re-soldered to prevent them tarnishing.
So, the PCM is back with the shop to continue the work. Hope to hear from them soon.
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Fleet Mechanic
Joined: Nov 2015
Posts: 1,838
Likes: 187
From: NoVA
Folks, It has been a while, but my Excursion is finally back up and running. I was away on vacation with the family. Here's a quick rundown on the troubleshooting and fixes that were done by the Ford Service tech.
- The PCM being unresponsive was the primary issue that we were dealing with. It was removed and sent to DTC (noted in prior posts) and came back as a perfectly working unit. But, after putting it back, we had made no progress and were still trying find the cause.
- Prior to taking the truck to the dealership, I had replaced all the fuses and relays in the fuse panel under the steering wheel to troubleshoot. One fuse was blown and that did bring power back to the OBD port, but there was no comms from the PCM.
- Tech pulled out a PCM from another F-Series and was successful in getting it to power up the PCM. Every test done was pointing to a bad PCM. So, decided to pull the trigger on a replacement PCM.
- This PCM powered up fine and started chattering and throwing out codes. Now we were able to take the next step in the right direction. The IDM relay blew immediately. A couple of electrical tests came back negative. Now, the dealership's electrical guru stepped in and started a hunt for potential broken wires, chafing, bad grounds etc. He did find a couple of cracked insulation, but nothing alarming. As a precaution, he did cleanup all the ground wires in the engine cavity. Now, after all of this, the last piece of the puzzle was a shorted out Fuel heater. Replaced that and the engine started up immediately on the first crank. The short apparently did a number on the PCM by back feeding ground through the IDM circuitry.
As part of all this troubleshooting, I did ask the techs to replace the major sensors that were potential culprits as pointed out in earlier posts - ICP, CPS etc. and provided them with Motorcraft spares in case they needed them. But at the end all of those spares are now back home and will go on the shelf as spares for another day.
I want take the time to thank @Nicmike and @Toreador_Diesel for keeping me sane as they guided me through all this. It has been a little over 2 months and I had even forgotten what the door codes were on my EX. But the almost daily chat with them over texts would reassure me that I just needed some patience and trust on my tech to get this EX running again.
Also, I want to give shout out to Joey (Service Manager) and Chris (Technician) at Koons Ford in Sterling, VA. They persevered through all this along with me and worked diligently to troubleshoot each of the existing and potential problems. If you are in the Northern VA area and are looking for a tech that knows his Diesels, talk to Joey and ask him to have Chris work on your truck.
- The PCM being unresponsive was the primary issue that we were dealing with. It was removed and sent to DTC (noted in prior posts) and came back as a perfectly working unit. But, after putting it back, we had made no progress and were still trying find the cause.
- Prior to taking the truck to the dealership, I had replaced all the fuses and relays in the fuse panel under the steering wheel to troubleshoot. One fuse was blown and that did bring power back to the OBD port, but there was no comms from the PCM.
- Tech pulled out a PCM from another F-Series and was successful in getting it to power up the PCM. Every test done was pointing to a bad PCM. So, decided to pull the trigger on a replacement PCM.
- This PCM powered up fine and started chattering and throwing out codes. Now we were able to take the next step in the right direction. The IDM relay blew immediately. A couple of electrical tests came back negative. Now, the dealership's electrical guru stepped in and started a hunt for potential broken wires, chafing, bad grounds etc. He did find a couple of cracked insulation, but nothing alarming. As a precaution, he did cleanup all the ground wires in the engine cavity. Now, after all of this, the last piece of the puzzle was a shorted out Fuel heater. Replaced that and the engine started up immediately on the first crank. The short apparently did a number on the PCM by back feeding ground through the IDM circuitry.
As part of all this troubleshooting, I did ask the techs to replace the major sensors that were potential culprits as pointed out in earlier posts - ICP, CPS etc. and provided them with Motorcraft spares in case they needed them. But at the end all of those spares are now back home and will go on the shelf as spares for another day.
I want take the time to thank @Nicmike and @Toreador_Diesel for keeping me sane as they guided me through all this. It has been a little over 2 months and I had even forgotten what the door codes were on my EX. But the almost daily chat with them over texts would reassure me that I just needed some patience and trust on my tech to get this EX running again.
Also, I want to give shout out to Joey (Service Manager) and Chris (Technician) at Koons Ford in Sterling, VA. They persevered through all this along with me and worked diligently to troubleshoot each of the existing and potential problems. If you are in the Northern VA area and are looking for a tech that knows his Diesels, talk to Joey and ask him to have Chris work on your truck.
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