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I have been testing both ways. so the BJB is the fuse box side of the C1035C connector yes? I am about to clip the corresponding pin 18 male prong right under the fuse box and run it straight to pin 1 on the APP
You need to test it. Remember this is 1 symptom not the symptom.

Do you have the BJB open? (Apart)
 

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yes, it is currently taken apart. I can see the APPVREF1 and APPRTN1 twisted together
Well if the bare pin is showing 12 VDC and you've got the BJB open trace it back. To the firewall it's a direct run to the APP. Short to voltage is going to be something that you're going to want to fix not just bypass.
 

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Discussion Starter · #44 ·
Well if the bare pin is showing 12 VDC and you've got the BJB open trace it back. To the firewall it's a direct run to the APP. Short to voltage is going to be something that you're going to want to fix not just bypass.
okay, I ran out of time to work on it tonight. I will trace it tomorrow and might grab a fox and a hound tool. I know you had referred to the BJB as its own device. Where are the relays for it located? I'm having troubles figuring out where it gets its 5V's from. I checked the same point on a friends ST and found that it isn't a 100% direct path.
 

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okay, I ran out of time to work on it tonight. I will trace it tomorrow and might grab a fox and a hound tool. I know you had referred to the BJB as its own device. Where are the relays for it located? I'm having troubles figuring out where it gets its 5V's from. I checked the same point on a friends ST and found that it isn't a 100% direct path.
VREF is provided by the PCM through the main engine harness. It only interfaces though the BJB C1035C to connect to things in the interior of the vehicle.

The BJB is the pass through for the APP. That's all. If the wiring met another connector or splice it would be listed on the diagram.

6 wire are running through the C1035C from tye APP to the PCM. Two potentiometers (power (VREF)and ground (RTN) to each and an output for each sensor back to the PCM.

One sensor is a High to low. 5 VDC on the output that decreases less than 1 VDC as the pedal is depressed.

And one is low to high. Less the 1 VDC on the output that increases 5 VDC as the pedal is depressed.

The two sensors are checked against one another to determine its position and the PCM controls the throttle body blade angle accordingly.

Two similar position sensors are located inside the TB.
 
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Discussion Starter · #46 ·
VREF is provided by the PCM through the main engine harness. It only interfaces though the BJB C1035C to connect to things in the interior of the vehicle.

The BJB is the pass through for the APP. That's all. If the wiring met another connector or splice it would be listed on the diagram.

6 wire are running through the C1035C from tye APP to the PCM. Two potentiometers (power (VREF)and ground (RTN) to each and an output for each sensor back to the PCM.

One sensor is a High to low. 5 VDC on the output that decreases less than 1 VDC as the pedal is depressed.

And one is low to high. Less the 1 VDC on the output that increases 5 VDC as the pedal is depressed.

The two sensors are checked against one another to determine its position and the PCM controls the throttle body blade angle accordingly.

Two similar position sensors are located inside the TB.
Okay, I am back out with the car this morning in AZ where it somehow rained last night. I did some tracing and didn’t realize the wires enter the firewall thru the passenger side of the car. I didn’t even know there was an entirely 2nd fuse box area.
 

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Okay, I am back out with the car this morning in AZ where it somehow rained last night. I did some tracing and didn’t realize the wires enter the firewall thru the passenger side of the car. I didn’t even know there was an entirely 2nd fuse box area.
BJB (battery junction box) - engine bay

BCM (body control module) - passenger side footwell

RJB (rear junction box) Hatch area
 

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Discussion Starter · #50 ·
Well if the bare pin is showing 12 VDC and you've got the BJB open trace it back. To the firewall it's a direct run to the APP. Short to voltage is going to be something that you're going to want to fix not just bypass.
I’m no longer getting that P2122 code. I wiggled the harness and no longer see 12+v and can’t find which side it had it on. I still have the same issues with limp mode with the only code P0453
 

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I’m no longer getting that P2122 code. I wiggled the harness and no longer see 12+v and can’t find which side it had it on. I still have the same issues with limp mode with the only code P0453
P0453 is vacuum in fuel tank high.
A stuck open purge valve can cause this to happen or a clogged Canister vent valve on the charcoal cannister.
 

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Discussion Starter · #52 ·
P0453 is vacuum in fuel tank high.
A stuck open purge valve can cause this to happen or a clogged Canister vent valve on the charcoal cannister.
I spoke too soon. I traced the entire wire and it’s not making contact anymore as long as the ecu isn’t plugged in. Once the ecu is plugged in, key on is when I start getting the accessory power from the battery in my pin 18 reading. That line seems to be fine. I checked from the C1035C connector to the ecu connector and nothing out of the ordinary.

this is a new ecu. Freshly programmed.
 

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So from PIN 1 APP to the male PIN 18 on the BJB (C1035C disconnected) are you getting continuity? Not voltage.
 

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Yes continuity is perfect from point A to point B
And if you turn the ignition to run is voltage present at either PIN 1 APP or Male PIN 18 on the BJB?
 

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Discussion Starter · #59 ·
SSgtjrrobinson's MASTERY of this car's electrical system continues to amaze me. The Mk 3 Focus ST is a cool little car for what it is and costs- but there are better cars. We are all fortunate that he chose to obsess on it, and not something else.
F’real!! If he is okay with it, I tend on sending him some money for his time and knowledge
 

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F’real!! If he is okay with it, I tend on sending him some money for his time and knowledge
I couldn't accept anything for what I do here because just like my day job, I sell Crack for the image, not the money.... But I digress.

If the male pin on the BJB and isn't showing battery voltage with the ignition on, and that wite has continuity between 18 BJB & 1 APP then you should be good on that side.

The next steps are you isolate the source of system voltage.

Start with the C1035C plugged in and PCM disconnected. Test PIN 12 on the PCM connector C1381B for voltage.

Font Material property Parallel Paper Rectangle

Font Material property Parallel Paper Pattern


It will has the same color wire as the the APP sensor. It is shows battery voltage we needed to look at the engine harness somewhere.

Let me know what you find before we more forward
 
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