Auto PCM with no Auto...

Charles · Jul 13, 2015

I removed the ability of my Ford PCM to run my trans shifting into the ground by installing a PCS on my 2002 crew cab and now I have two options for the engine control...

I already had a manual trans PCM for my year and had planned to switch to it, but apparently Ford decided to get cute and F' up the harness between auto and manual so that I'll have to re-pin at least the connector at the PCM to make that work, as it's stuck in some kind of limp mode because it thinks the coolant temp is high, plus the trans temp gauge on the dash is dead with a comfy red "Check Gauge" starring at me.

Otherwise..... the original auto PCM drives around fine except for a surging at certain load/rpm points, where I assume it's having some sort of separation anxiety about not being connected to the trans or something. It will run MFD from the 60's to the 20's, 60's, 20's over and over in rapid succession about once a second or so until you push through it with more throttle, or lift. It does it just the same on cruise control, and all the sensor readings I can view on the scanner are steady and stable.

So....

Since the truck drives nicely for the most part with the auto PCM and my harness is already working, plus I can still use the trans temp gauge I'm stuck with in my dash (by having the PCS send it a signal), does anyone know how to tell the PCM to STFU about the bs and just run the engine? Does anyone know what is making it surge the MFD repeatedly in the first place at certain load points? Is it trying to shift?

Any input would be great. At the moment I'm missing my 99-2000 stuff that gives no ***s...

If I have to repin this harness then a DAC PCM may be finding its way in. But I'd rather not dick with all that.

smokinstroker92 · Jul 15, 2015

Dieselboy would be the one to talk to about that, he runs a pcs controller on an auto 02 pcm. I have a pcs waiting to go in my 02 just no time to get it on

co04cobra · Jul 15, 2015

Running a manual PCM is about the only way I've found to stop that surge. The 02 trucks are a pita compared to 99-01.

If you run the AEB PCM and wire in a extra coolant temp sensor it wants, and tie it into the TFT sensor wire, it will take care of your light issues.

Here's a link I've used before.

http://www.powerstroke.org/forum/99...-wiring-solutions-02-03s-not-same-99-01s.html

Charles · Jul 15, 2015

co04cobra said:
Running a manual PCM is about the only way I've found to stop that surge. The 02 trucks are a pita compared to 99-01.

If you run the AEB PCM and wire in a extra coolant temp sensor it wants, and tie it into the TFT sensor wire, it will take care of your light issues.

Here's a link I've used before.

http://www.powerstroke.org/forum/99...-wiring-solutions-02-03s-not-same-99-01s.html

Well sh*t....

I thought about just placing a resistor on the TFT wire to make it STFU, but that still leaves my in-dash trans temp gauge dead with a big red check gauge light...

On the one hand it's nice to see I'm not the only one.... on the other.... that sucks...

Charles · Jul 17, 2015

Alright, if the consensus is manual PCM for sure.... then why is it necessary to add a coolant temp sensor to calm the high coolant temp issue?

In order of logic, I would think...

Turn it off in the code.

Place a resistor in the line with a reference source.

Tie into the existing coolant sensor output.

And dead last would be add a sensor you already have.

Have the other things already been tried and found ineffective?

Lastly, what was done about the dead trans temp gauge in the dash? Swapped to a man dash? Or locate the wire for the gauge and feed it what it needs to STFU at a minimum, or possibly actually WORK (novel idea right...) at best.

co04cobra · Jul 17, 2015

The manual PCM looks for 2 ects. Most of them in 99-01 did also.

You could probably put a resistor inline like you are saying to get rid of the P0118 code it will throw.

If you wire in another coolant sensor, tied into your current engine harness signal wire for the ect sensor already there, then also back to the TFT sensor wire on the inner fender it will shut the gauge on the dash up too.

I'm sure there are other ways to do it but the port for the extra ect sensor is already in the front cover and I had the pigtails and sensors laying around so that's what I did.

Charles · Jul 17, 2015

The TFT wire is run to the pin on the PCM connector where a man PCM is looking for ECT right?

Or does the TFT wire run to the GEM? Does the GEM or the PCM run the gauge in the dash?

I assumed running a voltage signal to the TFT wire with a man PCM in place would run into the man PCM as an ECT input, and the dash TFT gauge would remain dicked over.

IHPowerstroke7.3 · Jul 18, 2015

That is correct, same circuit is used. Looks like pin 37 at PCM, Orange/black. Auto PCM looking at TFT, Manual looking at Coolant Temp.

However it looks like the TFT signal is sent to the cluster from the PCM over the SCP network. Also there is a second coolant sensor that is wired direct to the cluster.

I would think it would be best to use actual coolant temperature as the input to the manual pcm though as it would have an effect on tuning, but I'm sure you're way ahead of me on that.

co04cobra · Jul 18, 2015

Sorry for the slow response been out of town, but like posted above, that is what I was pulling from memory.

It has been about a year since I was working on one.

I believe feeding coolant temp to pin 37 is what has been working.

Charles · Jul 19, 2015

Sending the man PCM a happy coolant temp voltage I understand would make it STFU about high coolant temperature. And I will take care of that however I need to, even if it means adding another redundant sensor.

What I don't understand is what makes the trans temp gauge in the dash stop showing zero temp with a "check gauge" light, or does the man PCM tell it to STFU whenever it gets a happy ECT reading?

Because on a man truck that gauge isn't TFT.... it's volts....

So I'm confused as to how the man PCM would ever make the TFT gauge happy.

Or is it like a posi-trac on a plymouth..... it just does.... lol

IHPowerstroke7.3 · Jul 20, 2015

I see what you're saying. The redundant sensor would only be used for the cluster which is only used on the diesel trucks.

I'm not sure what you could do about the tft gauge as the cluster would be looking for a signal from the auto PCM. Wiring a resistor in where tft sensor would be is obvious. Being the two read on the same pin at the pcm, man and auto respectively, the pcm would be getting a signal of whatever you want to give it. But I don't know how the cluster is going to get the signal from the man PCM.

Charles · Nov 2, 2015

Finally had time to dick with this.

Not knowing what resistance value ford might have used for the pull-up resistor in the pcm for TFT, I had to study the ford temp sensors and came up with a resistance value between 4 and 6 kohm in the 150ish degree range.

So I placed a 5 kohm resistor between pins 7 and 8 on the transmission solenoid pack connector and voila..... the manual trans pcm finally stfu about a coolant temp that no other 7.3 computer ever gave a solitary *** about in the first place...

Problem is, as suspected, the TFT dash gauge is now dead with a constant "check gauge" light next to it.

Now I have to locate the input to this, decipher what mode it is and see if maybe the PCS can feed it, which would be awesome because the pos might actually be useful instead of just another idiot gauge doing no good on the dash.

On Edit:

I initially configured a 10k pot with a couple 10k resistors stacked so I could simply vary the resistance on the TFT wire until 150 to 160 degrees was noted through the scanner, but alas..... the trans temp is an idiot gauge, and therefore, even though I could see the input voltage changing on the scan tool, the PCM always output 60 degrees as the TFT anywhere from around 2 volts to nearly 3.5 volts I was able to vary through. So forget picking a resistance value that way....

Charles · Nov 2, 2015

Alright, I was hoping to locate some kind of wire or something going to the TFT gauge, but apparently this is all microprocessor controlled and the communication to the dash from the PCM is all digital.....

So....

If some of you have seen the TFT gauge read correctly with a manual trans PCM I would like to figure out how. The man trans PCM shouldn't be outputting anything at all for the TFT gauge because a man trans truck doesn't have one, it has volts, which the dash reads itself, directly from the input voltage feeding the dash.

I'm still lost why the man pcm would activate the TFT gauge in the cluster...

Power Hungry · Nov 3, 2015

The problem with 2002/2003 7.3L when converting is that the IC gets several values from the PCM through the SCP bus. Since a M/T truck doesn't use a TFT sensor, the instrument cluster would not have that gauge and the firmware wouldn't look for a temp reading. The only suggestion would really be to fake a voltage to the TFT sensor circuit or install a M/T Instrument Cluster.

Charles · Nov 3, 2015

Power Hungry said:
The problem with 2002/2003 7.3L when converting is that the IC gets several values from the PCM through the SCP bus. Since a M/T truck doesn't use a TFT sensor, the instrument cluster would not have that gauge and the firmware wouldn't look for a temp reading. The only suggestion would really be to fake a voltage to the TFT sensor circuit or install a M/T Instrument Cluster.

I would actually love to install a manual instrument cluster as it would have a gauge that actually mattered.... volts.

I can't find one. Not new, used or otherwise.

If I'm stuck with this IC, I really need the TFT gauge to do something. Just sit in the middle like it did with the VDH PCM if nothing else. Dead gauges look like hell. Truck looks hacked. Pulling the bulb out of the "check gauge" light would be one thing but the gauge sitting on the bottom pin all the time looks like hell. I guess I could glue the sob in the middle, lol...

co04cobra · Nov 3, 2015

I should have a manual 02 instrument cluster. Ill shoot you a PM if I can find it Charles.

Charles · Nov 3, 2015

co04cobra said:
I should have a manual 02 instrument cluster. Ill shoot you a PM if I can find it Charles.

Man, that would be sweet. On the way home today I was actually going to see if the dealer could get one and if so..... god all mighty what they might want for it...

I miss volts. First gauge I looked at each time I keyed the truck on for over 15 years is a hard habit to break.

Let me know man.

Btw.... on my red truck I seem to remember only tying the start circuit wires together for the clutch safety switch and that gave me start and leaving the cruise control kickout wires unconnected let the cruise work.

This auto truck came with a neat little dongle that plugs into the clutch safety switch connector allowing the truck to crank with no clutch safety switch, but with the man trans pcm I now have no cruise. Today I removed the other pins in that dongle so that only the start circuit was still closed and still no cruise.

Is there anything else I'm missing for cruise? Haven't had a chance to check the scan tool, but it shouldn't be brakes or anything because all I did was swap in the man pcm and poof.... no cruise.

Thanks.

co04cobra · Nov 4, 2015

Here's that info copied from that previous link on the cruise wiring. I've used a good bit of this guys info on the 02 stuff and it seems to make most of it work.

That post is just on the cruise but he had more info on the TFT tying into the other ECT wire. I knew the factory manual trans trucks had 2 ECTs and the additional one went into the front cover. He put a another sensor close to the water neck, but other then that, I don't recall having to change much from what he had found.

Now on to making the Clutch Pedal Position Sensor (CPPS) and the Cruise Control work.

Even with the Manual Tranny PCM, the PCM still looks for the Range Sensor on the Auto Transmission to tell it what gear it is in. It uses this information for several different tasks, including starting and Cruise. You have to make the computer think its seeing the Range Sensor when its actually seeing the CPPS. Under the dash tucked up past the Clutch pedal, (its easier to find before you install the pedal), is the wiring harness for the CPPS. It has a plug in it that is called the "Triple Function Switch Jumper". It lets the harness exist, but not do anything because its not needed with the automatic. As far as I could tell, it doesn't do crap anyway. In Order for the CPPS to operate Correctly you will need to run some wires. There should be 6 wires that come into the connector. Personally I reached up in there and cut the harness about 3 inches back from the plug. This was so I could get it out from under the dash to work on it. There is only one wire that stays connected to the harness, and its much easier to add on to it than to work under the dash.

Here's what to do with the wires:

Red / Light Green - This wire will stay connected to the harness as it was from Ford. You need to make sure it has 12 volts on it in the run and crank position.

(2) Blue / Yellow - There are (2) of these on the switch. Connect them together and run them through the firewall to the Gray connector mentioned earlier for the water temp sensor.

Tan / Red - Run through the firewall to the Gray connector.

White / Pink - Run through the firewall to the Gray connector.

Those (3) Wires have corresponding wires on the wheel well at the gray connector. Cut those wires and attach the new wires from the CPPS the same way you did the Water Temp Sensor.

Personally I used a short piece of trailer wire so the wires would stay together and have different colors.

Tan / Light Blue - This wire is the Speed Control wire (cruise). It cancels the cruise if you push the clutch in. In the automatic, however,this wire cancels the cruise if you push the overdrive off switch. So you need to connect the TN/LB to the overdrive switch. To do this you will need to remove the plastic cover, top and bottom, on the steering column. under there you will find a set of very small wires that connect to a harness and go up to the overdrive off switch.
On the harness that the small wires are connected to you need the
Tan / White wire. It helps to remove the dash cover to get access to the wire. Cut the Tan / White wire at the harness and connect it to the TN/LB wire on the CPPS.

This is also a good time to remove the Auto's Shifter unless you desire to have two!

Personally at this point I tried it. Try to crank the truck with the CPPS off of the clutch. It should not crank. You can slide the CPPS back to simulate pushing the clutch in to see if your work has paid off. The truck should crank when you push the slide back. MAKE DAMN SURE YOU HAVE THE TRUCK IN NEUTRAL! At this point my truck did as I was hoping and I breathed a sigh of relief.

Now you can put the CPPS on the Clutch Pedal Rod and check your work one last time. Take it for a drive and get above 40 or so mph and try the cruise. Mine worked, and at this point I let out a nice little rebel yell!

Charles · Nov 4, 2015

Just figured out where I probably lost cruise after reading your post....

After I installed the PCS I quickly grew tired of seeing the OD off light blinking so I unplugged it at the column. Bingo.... apparently this is a part of the circuit for canceling cruise. I never knew an auto truck canceled cruise based on OD OFF....

Since those wires are unplugged inside my column that's probably where I lost the cruise circuit.

Now I'll have to see about getting another one of those cute little plastic dongles for the clutch safety switch plug now that I've killed two of the three connections in it.

Btw, inside that plastic dongle on the safety switch plug, there is continuity between the two corresponding pins of the 3 circuits in that plug, 2 wires per circuit.

Thanks man. I'm sure hoping you might be able to get your hands on a manual cluster...