While doing the RGP cleaning, found some issues
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Laughing Gas
Joined: Apr 2004
Posts: 776
Likes: 42
From: STL MO
Andy, from all I read so far, the Baro volt should be ~4.6V. According to Tugly, there is actually a Baro sensor inside the ECM that reads Baro pressure as a reference “Information it is: BARO is a sensor in the PCM for reference”.
If the voltage/pressure table he linked to is actually for EBP, then my 14.17 PSIa reading should be between 1.1 and 1.5V (11.5 and 14.7 PSIa). Instead, my reading is 0.87 V. So, something is not right here. If that table were for the MAP sensor, then it might make sense. However, I did not find a way to see the ECM volt reading on the MAP. To answer your concern, YES, those two voltage readings should be different. It's possible that the really MAP sensor voltage reading is the same as that of the EBP sensor. We'll figure it out soon.
After having installed the two new sensors last night, I did think of just stop here since I never experienced any drivability issues. However, I can’t stop thinking about it. Well, I have to follow Tugly’s command: “I wouldn't let it go... it won't get better with time”.
Before someone more resourceful than any of us comes aboard and give us the official Ford pressure/voltage table for both the MAP and EBP, Here is what I need from you guys if you can. At KOEO (key on engine off), measure the voltage at the sensor connector and report the following:
KOEO
1. Your location (altiturte) or the Baro as you know for the location
2. MAP reading __________PSIa
MAP sensor voltage_______Volts (at the connector not the Baro volts from the ECM)
3. EBP reading ___________ PSIa
EBP sensor ___________ volts (at the connector not the Baro volts from the ECM)
I’ll compile the readings once we have a few good ones. I believe this will give us a good direction to dif to the bottom of the MAP/EBP myth. Thx all. Eriwn
Thread Starter
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Laughing Gas
Joined: Apr 2004
Posts: 776
Likes: 42
From: STL MO
anyone know the wiring for MAP and EBP?
Poked around a little in the last half hour.
The MAP sensor connector is easier to do the reading from the back with long needle probes whereas the EBS not. I have to pierce through the wires.
Anyway, there are three wires on each sensor.
MAP sensor:
1. White w/ red tracer
2. Bright green
3. Brown with white tracer
Without knowing which is which I measured between all of them.
Voltage to ground: #1 0.024V (must be the ground)
#2 1.509V (could well be the signal)
#3 5.052V (power?)
Voltage to each other:
#2 to #1 1.484V
#2 to #3 -3.542V
Does anyone have the wiring diagram? I thought the I have one. Did not find it. Only found the 4 volume service manual for my old 95 truck. Let me know if you know the wire arrangement for both the MAP and EBP. Thx
The MAP sensor connector is easier to do the reading from the back with long needle probes whereas the EBS not. I have to pierce through the wires.
Anyway, there are three wires on each sensor.
MAP sensor:
1. White w/ red tracer
2. Bright green
3. Brown with white tracer
Without knowing which is which I measured between all of them.
Voltage to ground: #1 0.024V (must be the ground)
#2 1.509V (could well be the signal)
#3 5.052V (power?)
Voltage to each other:
#2 to #1 1.484V
#2 to #3 -3.542V
Does anyone have the wiring diagram? I thought the I have one. Did not find it. Only found the 4 volume service manual for my old 95 truck. Let me know if you know the wire arrangement for both the MAP and EBP. Thx
Thread Starter
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Laughing Gas
Joined: Apr 2004
Posts: 776
Likes: 42
From: STL MO
some preliminary conclusions and more questions
EBP Sensor:
1. grey (could be white) with red tracer
2. purple with blue tracer
3. brown with white tracer
#1 to ground 0.024V (must be ground, consistant with MAP)
#2 to ground 0.89V (must be signal wire)
#3 to ground 5.05V (must be power)
#2 to #1 0.866V (exactly the same reading as AE reading 14.1 PSIa)
My conclusions, remember it’s just mine. Might not be right.
Concerning my EBP:
1. My new EBP sensor generated 0.866V and my ECM sees exactly the same. This means no wiring issue. 2. My ECM interpreted as 14.1 PSIa which is somewhat consistent with where I am (under the Arch as Tugly called it). This means my new sensor and ECM are good.
3. HOWEVER, if the voltage is supposed to be around 1.5, then there is still a problem. We will wait to hear from someone.
Concerning my MAP:
My new MAP sensor generated ~1.5V (if the green wire is indeed the signal which I’m pretty certain). I don’t know what my ECM reads because there is no way of knowing that. It happened to match exactly 14.7 PSIa on Tugly’s table. However, my ECM interpreted as 12.7 PSIa which is obviously wrong for my elevation. So, What do I do about it?
1. grey (could be white) with red tracer
2. purple with blue tracer
3. brown with white tracer
#1 to ground 0.024V (must be ground, consistant with MAP)
#2 to ground 0.89V (must be signal wire)
#3 to ground 5.05V (must be power)
#2 to #1 0.866V (exactly the same reading as AE reading 14.1 PSIa)
My conclusions, remember it’s just mine. Might not be right.
Concerning my EBP:
1. My new EBP sensor generated 0.866V and my ECM sees exactly the same. This means no wiring issue. 2. My ECM interpreted as 14.1 PSIa which is somewhat consistent with where I am (under the Arch as Tugly called it). This means my new sensor and ECM are good.
3. HOWEVER, if the voltage is supposed to be around 1.5, then there is still a problem. We will wait to hear from someone.
Concerning my MAP:
My new MAP sensor generated ~1.5V (if the green wire is indeed the signal which I’m pretty certain). I don’t know what my ECM reads because there is no way of knowing that. It happened to match exactly 14.7 PSIa on Tugly’s table. However, my ECM interpreted as 12.7 PSIa which is obviously wrong for my elevation. So, What do I do about it?
Thread Starter
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Laughing Gas
Joined: Apr 2004
Posts: 776
Likes: 42
From: STL MO
Nail it! Final conclusions
A cheap Super Chips tuner came with the truck when I bought it and I don’t have the fund now to get a good one. I’ve been running a tune called “tow safe” ever since. I’ve been suspecting that it’s messing with the ECM to get false MPG readings. And, it occurred to me today that that stupid tune might be feeding my ECM with false MAP reading too. I immediately returned it to stock tune and did an AE reading. YES, that sucker is the culprit!!!
KOEO:
MAP 14.6 PSIa 1.509 V (at the connector with a DMM, NOT the Baro from the ECM on AE. The Baro is reading 4.57 V)
EBP 14.54 PSIa 0.90 V
So, here are the conclusions:
1. YES, Tugly is right that your MAP and EBP reading should be virtually the same at KOEO if everything is functioning right.
2. Your EBP input voltage should NOT match Baro voltage from the ECM, because the MAP and Baro might be two different sensors.
3. YES, the PSIa/V table from Tugly’s link is indeed for the MAP sensor
4. According to data from my truck, the EBP sensor has a different PSIa/V co-relation table which points the 14.54 PSIa to 0.90 V. Still need input from other members to confirm or overturn this in order to properly close the case.
So, it’s been fun to chase this wild goose (at least it seemed so at the beginning with my little experience in this subject matter). Thx all those who contributed along the way. Erwin
KOEO:
MAP 14.6 PSIa 1.509 V (at the connector with a DMM, NOT the Baro from the ECM on AE. The Baro is reading 4.57 V)
EBP 14.54 PSIa 0.90 V
So, here are the conclusions:
1. YES, Tugly is right that your MAP and EBP reading should be virtually the same at KOEO if everything is functioning right.
2. Your EBP input voltage should NOT match Baro voltage from the ECM, because the MAP and Baro might be two different sensors.
3. YES, the PSIa/V table from Tugly’s link is indeed for the MAP sensor
4. According to data from my truck, the EBP sensor has a different PSIa/V co-relation table which points the 14.54 PSIa to 0.90 V. Still need input from other members to confirm or overturn this in order to properly close the case.
So, it’s been fun to chase this wild goose (at least it seemed so at the beginning with my little experience in this subject matter). Thx all those who contributed along the way. Erwin
Hotshot
Joined: Jan 2011
Posts: 18,849
Likes: 179
From: Puget Sound
Please excuse my absence... my daughter (from Ballwin) visited here for a family matter. I'm back at the keyboard with bells on.
I've reviewed your hard work and I completely agree with your last post. I've learned it's not unusual for mass-produced chips to trick sensors to achieve some kind of goal. If you are running in "Tow Safe", reducing the MAP signal will defuel the truck a bit to lower EGTs. It also makes the truck whimpy.
Great job chasing this down! Now I'm curious what your economy will do when you just return it to accurate sensor readings.
I've reviewed your hard work and I completely agree with your last post. I've learned it's not unusual for mass-produced chips to trick sensors to achieve some kind of goal. If you are running in "Tow Safe", reducing the MAP signal will defuel the truck a bit to lower EGTs. It also makes the truck whimpy.
Great job chasing this down! Now I'm curious what your economy will do when you just return it to accurate sensor readings.
Thread Starter
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Laughing Gas
Joined: Apr 2004
Posts: 776
Likes: 42
From: STL MO
We can definately feel the void when you're not here. I'm glad too that it came to a closure. I have to keep using the towsafe tune from Superchips before I can afford a decent tunner. It get me ~15 mpg while the stock only 13 (plus stock runs very slugish). I'll see if there is any mpg improvement. Erwin
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