05 eating MAP sensors

[syrupdawg]

My 05 has been through 2 MAP sensors in the last 4 or 5 months. It starts out barely noticeable. Its always between 10-15 lbs of boost and eventually gets so bad it wont hardly fuel at all you have to ease around with no power. It feels like the truck pulls fuel out of the tune when it hits that boost level. Its extremely noticeable when towing or driving up a steep hill. I can be going and go to give it some fuel to hold speed and when it hits about 12 lbs of boost it falls back down to 10 lbs and I can keep giving it more and more pedal until it either comes out of it or downshifts. Once you get it past 15 lbs it goes on like it should.

I originally replaced the first MAP sensor and it drove great for a few weeks then it started doing it again. So I unplugged my MP-8 thinking it may have been going bad. After I unplugged it the truck did great for about 2 months now its doing it again slowly getting worse. Im thinking the MP-8 was just magnifying the problem.

Anyone got any ideas on this? I guess its possible I just got a bad MAP sensor the 2nd time.

 

[bones]

had this happen before and it was a bad mp8 harness. new one fixed me up. did you look to make sure that the pins in the plugs all fit correctly? a good dab of diatalic(im a spelling beech aint I) grease may be worth a try as well....

 

[syrupdawg]

its starting to do it again after I had the Mp8 unplugged. That's why I think the MP8 was just magnifying the problem

 

[bones]

yeah I understood that, try to grease to make sure its not a poor electrical connection.

 

[syrupdawg]

yeah I understood that, try to grease to make sure its not a poor electrical connection.

Okay sorry I miss understood you!

Also I forgot to mention in the OP, it doesn't set the Check engine light on until it starts getting bad but I can clear the code and it will drive right for a few miles then trip it again. It eventually gets so bad clearing the codes does nothing it just comes right back on.

 

[mysterync]

What is the failure? Is the sensor producing low or high signal voltage? Not working is not the failure, loss of power or ground could be the failure, a signal short to ground could be the failure. The code is only grounds for diagnosis not replacement.

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[syrupdawg]

What is the failure? Is the sensor producing low or high signal voltage? Not working is not the failure, loss of power or ground could be the failure, a signal short to ground could be the failure. The code is only grounds for diagnosis not replacement.

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The code its throwing is a voltage code. Im also getting a rail pressure sensor performance code. Its just recently started throwing that. Possibly what problem I'm having now instead of MAP sensor

 

[mysterync]

Sounds like you have Vref issues. Vref is the 5 volt circuits which typically feed sensors. In this case F855 (pink with yellow tracer) feeds the map/Iat and rail pressure. I would start by verifying that this circuit has 5v present and determine if the voltage changes with a wiggle test and then determine if it drops when the failure occurs. The easiest way to confirm would be a DSO on the circuit in question. You could have a faulty ecm, faulty tipm or a short to ground or open.

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[Snedge]

Sounds like you have Vref issues. Vref is the 5 volt circuits which typically feed sensors. In this case F855 (pink with yellow tracer) feeds the map/Iat and rail pressure. I would start by verifying that this circuit has 5v present and determine if the voltage changes with a wiggle test and then determine if it drops when the failure occurs. The easiest way to confirm would be a DSO on the circuit in question. You could have a faulty ecm, faulty tipm or a short to ground or open.

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Well well. Someone has done some homework. :Cheer:

 

[syrupdawg]

ill check that when I get a chance. I appreciate the answer! if anyone else has some suggestions Ill be glad to listen!

Im not much on these drive by wire engines! Even though Ashley is trying to convert me lol

 

[mysterync]

Sounds like you have Vref issues. Vref is the 5 volt circuits which typically feed sensors. In this case F855 (pink with yellow tracer) feeds the map/Iat and rail pressure. I would start by verifying that this circuit has 5v present and determine if the voltage changes with a wiggle test and then determine if it drops when the failure occurs. The easiest way to confirm would be a DSO on the circuit in question. You could have a faulty ecm, faulty tipm or a short to ground or open.

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Left out that the circuit also feeds the cam sensor if I remember correctly. I would check the splice for a fault first! A shorted sensor could pull vref down enough to cause a fault.

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[mysterync]

Well well. Someone has done some homework. :Cheer:

Just because its fresh on my mind, ive rewired a 06 from ground up this week thanks to someone's amateur wiring job lol

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[Spooler]

You need to check the wire running to the A/C high/low pressure switch. It will run by the AC lines off of the compressor and eventually chauff itself, shorting to ground. Take a look. It is feed off of the same 5V reference I think.