6.0 Reference Voltages in PCED

Bruce Amacker · July 2, 2009

Hey Guys:

As a regular matter of research, I commonly do pinout voltages and compare them to the OEM manual. I did a 2006 F350 auto 4wd truck recently and complied the data to share. Not surprisingly, there are considerable differences between what I read and what the OE prints. I could not find a pinout voltage chart in the PCED for the Transmission connector (C1381B). Is it hiding somewhere I can't find?

6.0 Reference Voltages

I have several concerns:

Pinout Inconsistencies- Irregularities

Connector C1381A (Body):

Pin A3 is shown in the Reference Values as Tripminder Fuel Economy, but in the schematics as 4WD Control Module.

Pin A27 shows N/A in Reference Voltages, but connector views shows it as Clutch Pedal Signal/Starter Interlock. Pin A36 is also Clutch Pedal Position.

Pin A31 (Cruise Control) shows contacts in the PCED Reference Values that do not exist: there is no “Set-“ or “Hold” button, and the truck has a “Coast” button which is not shown in the Reference Values. The voltages were also off by a country mile.

Pin A35 VSS voltages were off dramatically.

Pin A40 (KAPWR) showed .05v voltage drop measured against battery voltage, pin A46 showed .17v drop as it goes through the PCM power relay.

Connector C1381B (TCM):

Pin B1 shows “VREF” with a resistor inside the PCM, but it’s reading almost VBAT.

Pin B6 is shown as NA in the Reference Voltages, but shown as PTO RPM control signal in the connector view.

PCM: PCED shows grounds to be 0v, but there is never zero volts on an active ground. Voltages ranged in the .02 to .06 range for grounds.

Connector C1381C (Engine)

Pin C6 (Fan Speed Sensor) Schematic shows it should be 0v KOEO, but it read 11.95v.

Pin C9 is omitted in the PCED “not used” list (EEC schematics page 3 of 12), is not used in the system, but has 5.05v on the pin. IH has extra unused VREFs, and I’m wondering if Ford followed suit with an unused VREF.

Pin C15 is called out as an unused PTO control terminal.

Pin C16 is called out as an unused Battery Charge Protection Indicator Lamp.

Pin C33 (EGRVP) showed the EGR open slightly at idle.

Pin C23 (EGRVC) showed voltage higher than expected both KOEO and idling. EGR command was not checked in scan data at this time.

Sometimes the schematic calls for B+ but voltage measured is actually 1-2v less than B+. (Pin C3 GPCM)

Labeling a sensor ground as “Signal Return” causes a lot of confusion for a beginning tech. On the pinout sheet, I changed them to “Sensor Ground”.

Comments, clarifications, or experience with these circuits is encouraged.

Thanks!

slim · July 3, 2009

Alright I'll tackle some of this starting with the body connector C1381A which is labeled C1381B in the wiring diagrams, B for body connector.

Pin 3 is 4WD neutral switch sense, this is used to verify transmission range sensor indicates transmission is in neutral for engagement of 4WD low. Should indicate 0v in neutral and 5v in all other positions, this is switched using a transistor in the PCM according to the wiring diagram.

Pin 27 is clutch pedal starter interlock switch signal, and is used on manual transmission equipped only of course. Wiring diagram shows as VREF sensing circuit. Should be 0v with pedal depressed as depressing pedal closes switch and sends signal directly to ground (G101), and 5v with pedal released.

Pin 36 is speed control deactivation input from CPP switch, and is used to turn off speed control with clutch pedal depressed. Should read 12v with pedal released and 0v with pedal depressed and power for this signal is from fuse F2.45 10A in CJB.

Pin 31 is speed control switch input. Without knowing the size of the sensing resistor in the PCM I can't know what the voltages should be, but it does list resistances for each switch contact. On-1.11 ohms, Off-signal return, set/accel-600 ohms, Cancel-120 ohms, Coast-300 ohms, Resume-1.11 ohms. This doesn't seem right since On and Resume are the same resistances, and hitting on would resume and hitting resume would turn speed control on and I don't think that is how it operates but I have not tried. Also different year models show different switch configutations and I think they're all the same, I'm almost sure those values aren't right and you would have to measure these on a properly funtioning vehicle to have reference values. The pinpoint test doesn't have you do any electrical testing, it uses pid data monitoring to check switch inputs--oh well.

Pin 35 is VSS signal from ABS module. For some strange reason I can't open the PCED on PTS to access the diag process for the VSS signal. But according to the wiring diagram this signal is sent out by the ABS module and is shared with the radio, 4WD module, and windshield wiper motor. I don't have any idea what that should read, maybe a multiplexed binary code signal?

Pin 40 is listed as voltage supplied at all times(overload protected). It should be VPWR as it receives voltage directly from fuse F1.10 in BJB and is hot at all times. This should be listed as the KAM power.

I refer to B+ as a 12v regulated power used for sensors and VPWR as battery voltage, but B+ isn't as well regulated as VREF if that makes sense.

I hope that's what you're looking for and maybe that helped somewhat. If not let me know what was good and what was bad, I'll check on some of the other stuff if I have more time.

Bruce Amacker · July 3, 2009

Alright I'll tackle some of this starting with the body connector C1381A which is labeled C1381B in the wiring diagrams, B for body connector.

I'm not understanding you. Why do you refer to this connector as C1381B? I see C1381B as the 30 pin Tranny connector on the PCM in all of the schematics.

Pin 3 is 4WD neutral switch sense, this is used to verify transmission range sensor indicates transmission is in neutral for engagement of 4WD low. Should indicate 0v in neutral and 5v in all other positions, this is switched using a transistor in the PCM according to the wiring diagram.

Now I'm even more confused. The truck I tested is a 4wd, and pin 3 in the body connector read 11.26V KOEO and 12.75 KOER.

Pin 27 is clutch pedal starter interlock switch signal, and is used on manual transmission equipped only of course. Wiring diagram shows as VREF sensing circuit. Should be 0v with pedal depressed as depressing pedal closes switch and sends signal directly to ground (G101), and 5v with pedal released.

Pin 36 is speed control deactivation input from CPP switch, and is used to turn off speed control with clutch pedal depressed. Should read 12v with pedal released and 0v with pedal depressed and power for this signal is from fuse F2.45 10A in CJB.

Pin 31 is speed control switch input. Without knowing the size of the sensing resistor in the PCM I can't know what the voltages should be, but it does list resistances for each switch contact. On-1.11 ohms, Off-signal return, set/accel-600 ohms, Cancel-120 ohms, Coast-300 ohms, Resume-1.11 ohms. This doesn't seem right since On and Resume are the same resistances, and hitting on would resume and hitting resume would turn speed control on and I don't think that is how it operates but I have not tried.

My "On" voltage was 4.43V (PCED says B+) and my "Resume" voltage was 3.97V, (PCED says 4.7v) so the resistance in the switch is definitely not the same.

Also different year models show different switch configurations and I think they're all the same, I'm almost sure those values aren't right and you would have to measure these on a properly functioning vehicle to have reference values. The pinpoint test doesn't have you do any electrical testing, it uses pid data monitoring to check switch inputs--oh well.

Cool. That helps, but I'd still like to know way the Reference Voltage Charts show the voltages so far off of what I tested.

Pin 35 is VSS signal from ABS module. For some strange reason I can't open the PCED on PTS to access the diag process for the VSS signal. But according to the wiring diagram this signal is sent out by the ABS module and is shared with the radio, 4WD module, and windshield wiper motor. I don't have any idea what that should read, maybe a multiplexed binary code signal?

Once again, I didn't scope it (this time) and I don't have a saved waveform from that pin. The PCED Reference Voltage chart says it should be about 9v and I showed .16v. If it showed 9v I could believe a square wave digital signal, but at .16v I doubt it, unless there is no signal at 0MPH. If it were a digital signal, the voltage probably wouldn't be .16v at any speed.

Pin 40 is listed as voltage supplied at all times(overload protected). It should be VPWR as it receives voltage directly from fuse F1.10 in BJB and is hot at all times. This should be listed as the KAM power.

I refer to B+ as a 12v regulated power used for sensors and VPWR as battery voltage, but B+ isn't as well regulated as VREF if that makes sense.

"12v Regulated Power"- I'm not understanding this phrase. The only circuit I can see that this might apply to is TCM Pin 1 which they refer to as "Reference Voltage", but measures at 12.34v KOEO and 12.85v KOER. I can't remember seeing a 12v regulated reference voltage before this pin. If it were truly regulated at 12v, it would keep a lot closer to 12v than it is (like a typical VREF being within .05v of 5 volts).

I hope that's what you're looking for and maybe that helped somewhat. If not let me know what was good and what was bad, I'll check on some of the other stuff if I have more time.

This is exactly what I'm looking for- dialogue between the forum members on their interpretation of the circuits, along with any notes or experience with any of these oddball circuits. If Ford isn't going to tell us 100% truthfully what each of these circuits does and measures, we will (as a group) have to reverse engineer the trucks and come up with our own reference material. It will make us all stronger in the long run if we do.....

Thanks!

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slim · July 7, 2009

I didn't spend alot of time researching that stuff, I just looked at the wiring diagrams. So some of that is wrong and I'll look a little farther into it. The PCED's are working now.

Bruce Amacker · July 7, 2009

I'm actually looking for real life experience with these circuits to identify what is wrong with the PCED. I've got the PCED, too, and have identified many errors within it.

Certainly, some of the guys on this forum have either a notebook (virtual or real), scrappy papers with shit written on them stuffed into one of their toolbox drawers for future reference, or even .doc documents of notes they've taken. This is what I'm looking for, not an interpretation of the (wrong info within the) PCED.

I'm very disappointed with the amount of errors I've encountered in the PCED within a short period of time, and it shows the collective intelligence of the dealer techs who still manage to get the truck fixed, in spite of FMC giving them boatloads of bogus information in the PCED. IH has some errors and wrong voltages in their stuff, too, but I have to admit that I've found a lot more errors in FMC's info than in IH's info, and in a shorter amount of time.

With all of the guys wrenching on this forum on a daily basis, who has knowledge of actual operation of any of these circuits?

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Keith Browning · July 7, 2009

I am sure we all do Bruce but I personally haven't got much in the way of notes as far as these specific circuits are concerned.

As a side note, (no pun intended) I think any good tech is thinking about what he is testing and what he expects to see and why. I will try to keep this on the fore-front of my mind as I go about my work...

Unfortunately my dealership does not have the BOB adapters for these PCM's and taking actual readings off of the circuits is difficult to say the least when trying to back probe the connectors as I am sure you well know. Shit, scoping the CMP and CKP sensors has been a freaking circus act every time I need to do so. I have asked for the tool in the past but it still has not appeared on my workbench and with things the way they are at the moment it doesn't look like I will be seeing it any time soon. I am very surprised it is not an Essential Service Tool.

cbriggs · July 7, 2009

I agree with your side note Kieth, and i try to stress that to our apprentice, dont just follow the pinpoint test and answer the questions, What should you be seeing and why? I always print a wiring diagram fist and get an overview of the circuit in question. We were talking about errors int the pc/ed at a training course once, and i made the comment that we need to be smarter than the pinpoint tests. I think it was taken the wrong way, as i got some dirty looks, but its true. If all we do is read instructions and answer yes or no, then why do we need any "specialized " training at all?