PCM-Water/Oil Temp

[kawa]

Correct me if I'm wrong but I believe that Glow Plug "ON" duration upon cold start up is determined by the PCM reading the oil/water temperature of the engine.

QUESTION
Where is/are these temps obtained from? Is there a sensor in the oil/water jackets that sends this info to the PCM and if so, does anyone know where or how this is accomplished?

I can't seem to find the answer.

As always, thanks in advance.

Roger

 

[Double-S-Diesel]

pcm uses baro, oil temp and inatke air temp to cacluate glow plug on time.
also glow plugs stay on longer than the light.

 

[Mike]

Depending on what year your truck is the PCM had different strategies for the glow plug duration also.

Fill in your sig line so you can help us remember what you are driving Roger.

 

[kawa]

Sorry about the Non-Signature line, I'll fix that today. My truck is a 1997 2X4 Auto CC Short bed PSD 7.3 Red
Bone stock except for 3" DP no Cat stock exhaust.

Perhaps I worded my question wrong. Is there a "Sensor" that supplies this info to the PCM?

As always, thanks in advance,

Roger

 

[kawa]

Hopefully I have a signature now
Rog

 

[Mike]

Perhaps I worded my question wrong. Is there a "Sensor" that supplies this info to the PCM?

Yeah, its the sensors that Double-S mentioned. IAT sensor (intake air temp), baro sensor and the EOT sensor(engine oil temp). Based upon the info those sensors provide the PCM does several things upon a cold start, glow plug cycle is just one of them.

 

[kawa]

OK Mike I'm gonna tell ya my problem. I've been working on this for so long I don't even know when it started, but I'm gonna try and give you the readers digest version.

One day out of the blue upon starting my truck I get a CEL. It reads out as:
P-1395 & P-1396. Glow Plug Monitoring Fault Bank #1 & #2. With a digital ohm meter I had two (2) dead GP's one on each bank, both against the fire wall.

I replace all eight (8) GP's, CEL continues, Find burned terminal in one of the UVC gaskets, changed both gaskets and all UVC harnesses. Check the top of engine plugs velly, velly carefully. Look great. Get same CEL. Change GPR, some CEL. Double check all UVC gaskets for continuity, Good, Check all points for correct voltage, all good. End result, CEL. I have checked all the fuses, not just by sight but for continuity. Check good.

After my truck sets out all night, temps around 38-42* I will start the truck (right up) 30 seconds running I get the CEL. turn off truck, clear the CEL and for the rest of the day no matter I many start ups and stops I make....
No CEL...........

But I can drive home and park it and immediately check for codes and there they are but all day long (I assume, hate it when I do that) they just lay dormant and don't trigger another CEL.

None of this seems to affect the operation of the truck, it runs good and strong.

The long version of this is that I have had the VC's off three (3) times. I'm really getting quite good and fast at pulling those puppies.

I have checked, checked and checked again and I can't find what the hell is tripping those codes.

I have cleaned terminals, checked continuity of all the wiring that I can and nothing seems to help. Where it the PSD God when you need him?

I'm at wits end unless it's in the PCM.

Thanks for reading my ramble.
Rog

 

[Double-S-Diesel]

I would say PCM, never seen that code, and unless its a cali truck , or an x there is no monitor on the gp system.

according to the book, the codes only apply to cali trucks
but the short version of how it works is it sets a code on the bank reading less than 39 amps, or a short in the oposite bank.

Did ya replace the relay?

 

[kawa]

I would say PCM, never seen that code, and unless its a cali truck , or an x there is no monitor on the gp system.

according to the book, the codes only apply to cali trucks
but the short version of how it works is it sets a code on the bank reading less than 39 amps, or a short in the opposite bank.

Did ya replace the relay?

It is a Cali truck and I did replace the relay from Ford (expensive) i have a diagram of the relay and how it is wired. One of the small terminals goes to pin #101 (I think, can't find the diagram at the moment) I have to assume that this pin #101 goes to the connection at the end of the harness on top of the engine. that harness plugs into another connector and goes to where ever.According to your book then I must have a short in both banks (?)
Hmmmmmm!!!
Rog

 

[kawa]

DSD:
What book are you referring too? and when you say the there is less than 39AMPS from one bank it will set the CEL. 39 AMPS measured from where?

You really have my attention now but I don't know what exactly what you are talking about re the -39 AMPS.

Please advise, you just might have the answer if this dumb old man can understand what you're talking about.

As always, thanks in advance,

Rog

 

[kawa]

DSD:
What book are you referring too? and when you say the there is less than 39AMPS from one bank it will set the CEL. 39 AMPS measured from where?

You really have my attention now but I don't know what exactly what you are talking about re the -39 AMPS.

Please advise, you just might have the answer if this dumb old man can understand what you're talking about.

As always, thanks in advance,

Rog

Double-S-Diesel:
You must be a warlock or something becuz you no sooner mentioned declining AMPs I get two (2) additional codes: P-1391 & P-1393 which are: GP Circuit Low Input Bank #1 (RH) & same for Bank #2 (LH)

Now these new codes are right in line with the original codes of P-1395 & P-1396 which are: GP Monitor Fault Bank #1 (RH) & Bank #2 (LH)

I just don't know where to look to locate this problem. Do you? I sure hope so. Thanks in advance,
Rog

ps
Anyone else want to chime in pls do so.

 

[Double-S-Diesel]

I am using the ford repair manual, for 99+ SDs, got the little one from ebay and the big one from motors.
Koeo do you have a p0380 code?

 

[kawa]

I am using the ford repair manual, for 99+ SDs, got the little one from ebay and the big one from motors.
Koeo do you have a p0380 code?

Negative, I generally just get P-1395, P-1396 & P-1000. I just recently got the P-1391 & P-1393 plus I lost the P-1000.

I don't know what you are talking about re less than 39 AMPS from one of the banks. Where is this reading taken from?

Thanks for your help,
Rog

 

[Double-S-Diesel]

reading is taken from the wires feeding each bank off of the relay

p1000 ignore this code, not helpful at all on a diesel

next step. KC8
eot below 55degrees
koeo chek from clow plug relay shunt with is center terminal
to battery ground should have batt voltage for at least 30 seconds.
yes then
check all glow plug resistance, shuld be 2ohm or less.
if no pull covers and check connections.

then disconect all valve cover plugs, and install breakout box, leave pcm disconnected.
check resistanbce from right back gp plugs to pin 9 on the bresakout box
all readings 2 be within 2 ohms of each other.
if no look for short if yes
check pins on left side to pin 34
if no look for short if yess
check center pin shunt glow plug relay to pin 8
less than 2 ohms no look for open, if yes
check all gp circits above within 2ohms from bank to bank
check all 4 on right to pins 8,9,34, and all on left to 8,9,34
all values with in 2ohm replace pcm
not within 2 repair open in the highest circuit.
good luck

 

[kawa]

reading is taken from the wires feeding each bank off of the relay

p1000 ignore this code, not helpful at all on a diesel

next step. KC8
eot below 55degrees
koeo chek from clow plug relay shunt with is center terminal
to battery ground should have batt voltage for at least 30 seconds.
yes then
check all glow plug resistance, shuld be 2ohm or less.
if no pull covers and check connections.

then disconect all valve cover plugs, and install breakout box, leave pcm disconnected.
check resistanbce from right back gp plugs to pin 9 on the bresakout box
all readings 2 be within 2 ohms of each other.
if no look for short if yes
check pins on left side to pin 34
if no look for short if yess
check center pin shunt glow plug relay to pin 8
less than 2 ohms no look for open, if yes
check all gp circits above within 2ohms from bank to bank
check all 4 on right to pins 8,9,34, and all on left to 8,9,34
all values with in 2ohm replace pcm
not within 2 repair open in the highest circuit.
good luck

DSD:
I understand everything that you wrote except what is the
"Breakout Box?"and what is "KC8"?

One more thing, Are the pins numbered at the ends of the plugs? and if not is there a special way of Identifying them?

And my friend, I thank you ever so much for the help.

HAPPY NEW YEAR??

Roger