greenworks

Hey fellas got a intersting one, if I check the voltage on the power or (orange wire) on the map harness to ground with the batteries off, and key on as described in the book I get 12.5 volts and the book says it should be five, I tested 2 ecms and both get the same thing is the book a misprint, they elude to a bad ecm but I doubt both my stock ecm and the mad ecm are both bad?What would high voltage do to a map reading and fueling/boost, I think the way I understand it is the higher the voltage the more boost is present therefore probably reducing fuel or am I off base with that?

I am having problems finding a low boost condition with no leaks and even disconnecting and blocking the wastgate I only see 34 psi at 1500+ egt ....BD replaced the turbo last week suspecting that but same thing. I am stuped the truck runs great other than a little hot when playing. I have disconnect everything I have tried a new comp box every thing the normal guys check for..

Been chasing this for the whole summer with no avail, I may be forced to unlpug everything and get a diagnostic at Dodge.... which at our local dealer I might as well get the local Mary Kay lady to do it

j

tmleadr03

The way the MAP sensor works is basicly a variable resistor. You should have three wires going to it. Power, signal and ground, all going back to the ECM. Power in should be 5V power out should be 0V due to the voltage drop over the resistance. The third line is connected to a variable resistance so the voltage will change from 5V down to ~.5V depending on the Manifold Absolute Pressure. I am astounded that the MAP is getting 12.5 since that much voltage should fry the ECM completly. All MAP sensors are the same, BMW Dodge or Ford so this is how it should be as far as I know.


Have you tried replacing the MAP sensor?

I just confirmed through the service manual that suply voltage is indeed 5V. If you are getting more then that to the MAP the MAP is fried and you should replace, thing is there is something upstream that needs looking at before you replace it so it doesnt get the 12.5V again and fry again.

rockwithjason

test the voltage at the ecm and see if it is 12.5. then look for a short to anouther circuit in the wiring harness.

greenworks

I have replaced the MAP this spring, but to test they tell you to take of the harness to the map to test the voltage so that would exclude the sensor right or should I test it with the sensor plugged in. Where on the ecm would I test, just find the same orange wire with tracer and test it there or what. I hate electrical problems I guess the simple way even if dodge was incompatent (sp) would be to put it on the scanner that would find the problem right??

tmleadr03

The scanner will tell you some info if you have a check engine light on. If you ask the dealer to check your codes they will probably try to bill you for the labor (crazy since it takes 5 min, but they will bill you 1 hour). If you have anything like autozone or something like what we normal countries (non canadian ) have you can have the codes checked with out a charge though.

Your ECM should only be getting 5V itself. There is no way for it to be giving out more if its only getting 5V. Check pin 48 and 50 for power in and pin 3 for power out. Pin 48 adn 50 are fused (B+) so that should be power suply. Pin 3 is 5V supply to the MAP. If I am reading the diagram right. Make sure you are GROUNDED when you mess with the ECM, or your static charge will fry the computer. Pick up a grounding braclet at some computer store.

I will double check and get back to you.

tmleadr03

Ok, I double checked with someone a bit more experianced.

If you are getting 12.5V at the MAP it could be the voltage regulator in the ECM. Usually they go bad and you dont get all the voltage you are supposed to but they can also give too much. Check your intake air temp sensor and see how many volts its getting. If its high it definantly the voltage regulator gone bad. If that is good, then you could have a short to voltage somewhere. Trace the power from the ECM to the MAP and see if that is it.

How to fix if its the voltage regulator? Easy way is buy another ECM. Harder way, but cheeper, is to find someone who repairs and builds there own computers. Ask him to open up the ECM and replace the voltage regulator. You will then have to replace all affected sensors (they will be fried from the excessive voltage).

greenworks

I have a scanner and the ecm shows no codes, I also have 2 ecms and both do the same thing that is what troubles me. when you say test pins 48 and 50 where are those do you have a schematic for the ecm of are they numered I never noticed.... and can you test these with the harness off or simply find the wire and poke it with a multimeter. Grounding using a braclet ? explain that please not really elctronically ionclided as far as computers go.Thanks for the help!

Also would the truck run good and throw no codes at all with a pooched ecm?

Oh i will leave the "normal" country alone...... people who live in glass houses

greenworks

Ok more head scractching if I test with the batteries negative off and test from the neg post to the negative cable I also get 12.5 volts I am missing somthing or simply not thinking right

tmleadr03

Hmmm... First off. No codes, truck runs fine

Did you disconnect both batteries? And you shouldnt get a voltage reading from the negative to the negative. I think it might be time to test your Voltmeter on something else known.

greenworks

Yep both batteries off and two different multi meters same thing, what I suspect is I have a small leak to ground somewhere and I haven't got an idea as to what amperage of a leak but it is very small based on no drawdown. Will have to do some figuring I have my head mechanic at my golf course working on it also he has over 30 years of heavy duty mechaincs and he also baffled right now, I am, tanking in more info tommorrow hopefully something pops up.

greenworks

I found the problem...... haynes manual, I talked to BD and they test with the batteries connected. The manual says to unhook with the batterys hooked everything is fine guess I am looking again for another problem elsewhere. This is the third time I have found issues with the haynes manual, I ordered a factory cd tonight of the web.

Jason

tmleadr03

Yah, that is what I am going off of and it has the pin location of the plugs and such.