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-   -   No connection to pcm (https://www.thedieselstop.com/forums/f23/no-connection-pcm-656516/)

05-350 08-20-2019 10:23 PM

No connection to pcm
 
So I was driveing my 05 f350 down the road and out of nowhere it shut down. It wouldnt crank over or anything and the milage, trip, distance to empty, and fuel economy wouldnt pull up on the dash. When you hit the brake it throws a tbc code. So I tow it home and check all the fuses and relays and they are all good. I have a friend with a snap on computer plug into it and see what it says and it says it has no connection with the engine data sensor or trans sensor so he tells me maybe the pcm died. So I buy a new one and stick it in and it's doing the same thing. I did the thing I probably shouldnt have and disconnected the pcm entirely and it dosent change the symptoms I'm haveing. So I'm at wits end with this thing. Not sure where too turn too. I was told by the previous owner that it has one of those silly key fob imobalizers but that it's never worked so I've just left it in the door just in case. I changed the battery on the fob and it dosent do anything. I'm not against takeing the imobalizer out but I cant find the thing to remove it. Wondering what else to check before I start tearing into the wireing harness. I did a visual check on as much of the harness as I can and I dont see any spots where the look is damaged but I'm not sure if there is any common places where wires like to short out on these trucks. Any help is greatly appreciated because I have no idea what I'm looking for. I'm a 12v cummins guy trying to enjoy the luxury of a newer ford and I'm not enjoying it right now lol.

bismic 08-21-2019 04:27 AM

It could very well be the key fob immobilizer. Cheapest thing would be to remove it.

IMO the most likely issue is the Instrument Cluster (HEC) itself.

05-350 08-21-2019 07:12 PM

It's a brand new gauge cluster so I'm not sure that's it either. All the gauges work. I'm not sure where to find the imobalizer so if anybody has any idea where it might be let me know.

bismic 08-21-2019 08:15 PM

Well, the mileage, miles to empty, etc are part of the Instrument Cluster, so it doesn't all work.

05-350 08-21-2019 09:05 PM

Yes but it also says no connection to engine data sensor and transmission temperature sensor and wont crank over and wont start when you jump the starter or run the fuel pumps or anything. I found out the thing I thought was a imobalizer was a GPS tracker so I got rid of it. I also unplugged the pcm entirely and checked and I have no power at the pcm plugs. All the fuses and relays are good and literally everything else works. Really weird.

bismic 08-21-2019 10:04 PM

The relationship between the Instrument cluster and the PCM is the 5 volt reference circuit. Even the battery saver circuit failing in the instrument cluster can cause a no-crank. If the battery saver circuit is bad, it can cause a total loss of electricity (lights, horn, ignition, dash, fuel pump, starter, etc) or a partial. Just turning on the head lights for a few seconds can sometimes return the proper operation.

Often times fuse F2-22 is a culprit of a no-crank, but not necessarily the main cause. Most of the time F2-22 "pops", there is a problem that causes it!

In addition to a bad instrument cluster, a shorting out fan clutch can cause the no-crank, but will not impact the mileage and fuel economy display. Same w/ some of the 5 volt engine sensors. Disconnection of these can restore the cranking if the problem is with one of them.

Fan clutch
EGR valve
Mass Air Flow (MAF) sensor
Fuel bowl heater (if your model year has one)
EBP sensor

Background info - The fan clutch is wired with the transmission range indicator. If the fan clutch is shorted, which can happen a lot, it takes out the range sensor so the PCM doesn't know what gear it is in, therefore does not engage starter.

Also - The forward-most PCM connector (called the C1381b connector) contains the transmission solenoids, speed sensors, range sensor and TFT sensor wiring. Maybe a short in that cable/wiring.

bismic 08-21-2019 10:16 PM

Quote:

Originally Posted by 05-350 (Post 4666432)
It's a brand new gauge cluster so I'm not sure that's it either. All the gauges work. I'm not sure where to find the imobalizer so if anybody has any idea where it might be let me know.

So where did this brand new cluster come from? Is it a Ford part or aftermarket? Did these symptoms start happening after this "new" cluster of did you just forget to mention in post #1 that you tried a new one as a fix to the problem?

I wouldn't recommend a new cluster anyway. Sending the old one to CircuitBoardMedics is a better choice.

05-350 08-21-2019 11:46 PM

The cluster is a brand new Ford one from my understanding. I bought the truck with it already installed and the previous owner installed it December of last year. I will check the sensors and see if messing with one of them works. Thank you for giving me a starting point. Very new to these trucks so any help is greatly appreciated

05-350 08-21-2019 11:47 PM

The original reason the cluster was replaced was because the speedometer wasnt functioning

bismic 08-22-2019 07:00 AM

Probably not possible since you bought it used, but I would be wanting to know for sure where the installed cluster came from (and what model year it was for).

I understand the hesitance to suspect the cluster, especially after incurring the cost of a PCM that didn't help. That is why I posted the CircuitBoard Medic suggestion.

When you say you unplugged the PCM entirely and have no power at the plugs, please describe which PCM connector you are referring to and which pins you tested.

Let us know what you find inspecting the sensors I posted and trying to crank and start with them disconnected. Specifically look over the fan clutch wiring. Sometimes it gets damaged (or destroyed) by the fan blades.

Also double check fuse F2-22 (#22 under the dash).

PCM relay 302 under the dash also might be a possibility.

Lastly - please confirm whether or not the fuel pump runs w/ the key on (not when trying to crank).

Sometimes I have heard of the entire junction box under the dash having electrical problems. Usually that is centered around the integral fuel pump relay, but not always. Some have had even more issues than that.

05-350 08-22-2019 07:37 PM

I just confirmed with the previous owner it is a brand new gauge cluster from ford. I will dig into the sensors tonight and see if I can get it too at least do something.

bismic 08-22-2019 08:26 PM

Quote:

Originally Posted by bismic (Post 4666466)
Probably not possible since you bought it used, but I would be wanting to know for sure where the installed cluster came from (and what model year it was for).

I understand the hesitance to suspect the cluster, especially after incurring the cost of a PCM that didn't help. That is why I posted the CircuitBoard Medic suggestion.

When you say you unplugged the PCM entirely and have no power at the plugs, please describe which PCM connector you are referring to and which pins you tested.

Let us know what you find inspecting the sensors I posted and trying to crank and start with them disconnected. Specifically look over the fan clutch wiring. Sometimes it gets damaged (or destroyed) by the fan blades.

Also double check fuse F2-22 (#22 under the dash).

PCM relay 302 under the dash also might be a possibility.

Lastly - please confirm whether or not the fuel pump runs w/ the key on (not when trying to crank).

Sometimes I have heard of the entire junction box under the dash having electrical problems. Usually that is centered around the integral fuel pump relay, but not always. Some have had even more issues than that.

See previous question (in bold) above.

With regards to sensors, I would start w/ the fan clutch (check wiring for damage and if you find none, try starting w/ it disconnected). Keep wiring away from the fan blades. Then I would try the EBP sensor.

Then double check F2-22 and Relay 302.

You might as well verify that the fuel pump inertia switch hasn't activated also.

05-350 08-22-2019 10:03 PM

Well it was the fuse. I thought I checked them all but I guess not. Feel so stupid but thank you very much for your help. I appreciate more than you know

bismic 08-23-2019 07:29 AM

Glad you found the bad fuse. Keep in mind that often times a fuse blows, there is something that caused it. Most times it is the fan clutch and/or its wiring that blows that fuse, but the other things I listed can cause it as well.

Also, the "mileage, trip, distance to empty, and fuel economy wouldn't pull up on the dash" issue is NOT due to that fuse. So you may be dealing w/ that again at some point in the future.


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