My truck ran yesterday, but not today

Tiny
IMAKEORPHANS
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Ill get that for ya real soon. By the way, I accidentally flag your last post for review. Sorry, my phone is a little touchy
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Monday, November 7th, 2011 AT 1:40 AM
Tiny
SATURNTECH9
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The code is for map sensor high voltage so the computer thinks the engine is under a greater load then it is thats why the engine is loading up with fuel. Also did you inspect all the wires to the map sensor to make sure the wires arent shorted together?Dont worry about the flag for review they will figure out you hit it by mistake.
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Monday, November 7th, 2011 AT 1:53 AM
Tiny
IMAKEORPHANS
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I tested the ecm wire going to the map sensor, without the engine running, and got approximately 5 volts. I got.2 volts from the sensor. Strange thing is, I'm getting voltage to the ground!

I placed the red lead of my multimeter on the map sensor ground and the black lead on the outside cover of my alternator and got 2.35 volts. The wires to the map s. Look intact but perhaps voltage is bleeding somewhere. Should I just run a new seperate ground to my sensor or try to locate the short?
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Tuesday, November 8th, 2011 AT 2:49 PM
Tiny
SATURNTECH9
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So your getting voltage to the wire that goes back to the ecm that shows it as a ground inside the ecm?If thats the case then there is your problem if you run a new wire it has to go from the ecm ground like shown in the diagram and then back to the sensor. Not just to chassis ground or you can just try to see where there is a partial connection between the 5 volt refrence wire and the ground coming from the ecm. So iam correct on what is going on with which wire you found with voltage?
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Tuesday, November 8th, 2011 AT 5:15 PM
Tiny
IMAKEORPHANS
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You were right. I found 4.97 volts coming from the ecm according to the diagram. My Chilton manual says that a low.2 volts from the map signal wire is normal.

I'm worried about this ground wire because according to the diagram, that is a COMMON ground. What else, besides my map sensor is recieving voltage through this ground wire
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Tuesday, November 8th, 2011 AT 5:40 PM
Tiny
SATURNTECH9
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Alright the grey 5 volt refrence to the map splits off and also feeds the tps and the linear egr valve 5 volt refrences. The ground to the map sensor only splits off to the coolant temp sensor the purple wire to it. See if the purple wire to the coolant temp sensor also has battery voltage to it.I also posted a couple of wire diagrams so you can see how the wires split off and where they go.
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Tuesday, November 8th, 2011 AT 6:36 PM
Tiny
IMAKEORPHANS
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The coolant temperature sensor also has voltage on the ground. This voltage is how the computer determines the temperature I believe. Am I correct when I say that, according to the diagram, the MAP sensor is supposed to have voltage on the ground?
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Wednesday, November 9th, 2011 AT 1:06 PM
Tiny
SATURNTECH9
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Why would you have power to the ground side of the map sensor are you checking these wires with the sensors unplugged I hope?The purple wire comes straight from the ecm it shows that wire is grounded inside the ecm. Then it splits off to the purple wire to the coolant temp sensor. The grey wire to the map sensor shows it as a 5 volt refrence so that should have power then it splits off to the tps and egr. The power to the wires that are suppose to be ground would explain the problem you had with the map sensor and the coolant temp sensor which you replaced.
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Wednesday, November 9th, 2011 AT 4:25 PM
Tiny
IMAKEORPHANS
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I guess I'm a little confused about how the computer can read the coolant sensor if it is only sending a reference voltage out and not receiving a signal back from the sensor in the form of voltage.
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Thursday, November 10th, 2011 AT 12:21 AM
Tiny
SATURNTECH9
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The coolant temp sensor has a ground feed thru the purple wire and the yellow wire is the sensor signal to the ecm. Based on temperture the coolant temp sensor changes resistance so that changes the ground value from the purple ground wire so that way the ecm knows what temp the coolant is.I hope that makes it clear for you how it works.
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Thursday, November 10th, 2011 AT 3:51 AM
Tiny
IMAKEORPHANS
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That explains it. I didn't unplug the coolant sensor when I tested the MAP sensor ground. The voltage I got at the MAP ground was actually the coolant sensor's ground feed because their grounds are connected. I guess I will move on and test the Throttle position sensor.
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Thursday, November 10th, 2011 AT 4:42 PM
Tiny
SATURNTECH9
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Were getting a code for high map sensor voltage I would start there with that code.
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Thursday, November 10th, 2011 AT 4:49 PM
Tiny
IMAKEORPHANS
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I decided to attach a vacuum hose to my FPR and reduced the fuel pressure to 30 psi. The truck started right up and idled very smoothly. I reset the trouble codes to see if code 33 remained and it didn't. I got a new code 45 for a rich condition but that is redundant. I will test the vacuum supplied to the FPR to make sure there are no restrictions and then I will run datamaster to see what the computer is reading. I have not learned how to read a datamaster readout yet, could you please help me to decipher? I think the computer is holding the injectors open too long and datamaster may tell me why.
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Monday, November 14th, 2011 AT 4:49 PM
Tiny
SATURNTECH9
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Alright a couple of things here lets get back to your map sensor what ever happended to that?Also with all the sensors plugged in but the map sensor do you have the 5 volt refrence and the ground wire being ground like you should?If not we need to start there. As far as your fuel pressure regulator what is the vacuum reading to it at idle?
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Monday, November 14th, 2011 AT 5:06 PM
Tiny
IMAKEORPHANS
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The map sensor has been replaced. When the MAP sensor is the only sensor unplugged, there is a 4.99v reference to the MAP sensor, a reading of.02v from MAP signal, and approx. 2-3v on the ground. The 2-3 volts is coming from the coolant temperature sensor because it is connected to the MAP ground.

The fuel mpressure regulator reads 40psi at idle with the vacuum hose attatched. I set the FPR to 30 psi to get the engine running.
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Monday, November 14th, 2011 AT 7:09 PM
Tiny
SATURNTECH9
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The ground wire to the map sensor shouldnt have voltage to it period sounds like the power is shorted into the coolant temp sensor signal wire and is comint thru the coolant temp sensor. In the wire diagram it doesnt show a 5 volt refrence coming from the ecm to the coolant temp sensor. It shows a refrence wire the way the coolant temp sensor works is one side of the sensor has ground from the ecm. That goes thru the coolant temp sensor and as the sensor changes temperture from coolant it changes resistances value. So the resistance change is inputed in thru the other wire to the coolant temp sensor the signal wire. That goes back to the ecm so it can use that change to tell what temp the coolant is. So there shouldnt be voltage there. Because that would throw off the coolant temp sensor reading and the map readings. Like I said before that would explain the map and coolant temp sensor issues you had with it.
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Monday, November 14th, 2011 AT 7:55 PM
Tiny
SATURNTECH9
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Alright I must have been half asleep this morning when I said there isnt voltage to the coolant temp sensor the one wire is a shared ground and the other is a 5 volt refrence from the ecm. Thats what I get for just waking up and answering questiins while iam in bed. Do you you have a scan tool that can read live engine data on that car?
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Monday, November 14th, 2011 AT 11:07 PM
Tiny
IMAKEORPHANS
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Don't worry about it.
I have datamaster and will be using it to get a live readout of what the ecm is doing. Hopefully I can pinpoint the signal that is throwing the computer off and causing it to flood the engine. I will send the printout when I get it.
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Monday, November 14th, 2011 AT 11:17 PM
Tiny
SATURNTECH9
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Alright get me one of it idling and with the key in the run position and engine off.
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Monday, November 14th, 2011 AT 11:22 PM
Tiny
IMAKEORPHANS
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Hi, I just wanted to give you a quick update. Upon further inspection, I found out that the intake tube that goes from my air filter to my turbocharger was cracked all the way around. I replaced it with a cold air intake system and started the truck.

The truck runs perfectly! No need to reduce the fuel pressure. I am not sure if the intake could not have caused the problem I was having, but my truck has been running fine for the last 2 days so I will won't worry about the problem until it comes back. Thank you for all your help, you have kept my sane through all of this!
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Monday, November 21st, 2011 AT 11:00 PM

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