MAP Sensor Voltage Low

jmoomaw · **Posted:** Thu Sep 25, 2008 5:57 am

I cleaned off the Map Sensor. Soaked it, scrubbed it with a tooth brush, soaked it some more. Four hours later it was clean with just a few spots of tar that are very persistent.

I cleared the codes and within 10 miles threw a PO107. Low voltage means High Vacuum and rich fuel correct?

Could this be the result of cleaning because the ECU has stored the information and it will take time for the "learning phase" to correct itself? It has been a least a week.

JIm

fastRob · **Posted:** Thu Sep 25, 2008 8:27 am

jmoomaw wrote:

I cleaned off the Map Sensor. Soaked it, scrubbed it with a tooth brush, soaked it some more. Four hours later it was clean with just a few spots of tar that are very persistent.

I cleared the codes and within 10 miles threw a PO107. Low voltage means High Vacuum and rich fuel correct?

Could this be the result of cleaning because the ECU has stored the information and it will take time for the "learning phase" to correct itself? It has been a least a week.

JIm

Is it plugged in?

jmoomaw · **Posted:** Thu Sep 25, 2008 8:46 am

fastRob wrote:

jmoomaw wrote:

I cleaned off the Map Sensor. Soaked it, scrubbed it with a tooth brush, soaked it some more. Four hours later it was clean with just a few spots of tar that are very persistent.

I cleared the codes and within 10 miles threw a PO107. Low voltage means High Vacuum and rich fuel correct?

Could this be the result of cleaning because the ECU has stored the information and it will take time for the "learning phase" to correct itself? It has been a least a week.

JIm

Is it plugged in?

Fair question...and yes, I thought of that. I unplug it and replugged it in. I will clear the codes again.

I am also interested in the two questions below:
1. Does Low Voltage mean rich mixture? I know it means high vacuum....
2. Is there a learning phase in the ECU?

Thanks..
Jim

linewarbr · **Posted:** Thu Sep 25, 2008 10:43 am

n00b here. What do you soak the MAP sensor in, and how do you clear the codes?

ATXKJ · **Posted:** Thu Sep 25, 2008 11:27 am

Quote:

"jmoomaw
I am also interested in the two questions below:
1. Does Low Voltage mean rich mixture? I know it means high vacuum....
2. Is there a learning phase in the ECU?

Thanks..
Jim

1) Diesels do not pull a vacuum - you go from Atm pressure to Atm+ ~15 psi boost - no vacuums
also there are no rich/lean mixtures - it always has more O2 that it needs - the fuel injected controls the engine speed/power.
2) There is a learning cycle - if you disconnect the battery for a while (not sure how long)- it will clear the memory and you have to relearn standard driving - however while it's relearning - you have the defaults - so no CEL due to that.

nursecosmo · **Posted:** Thu Sep 25, 2008 11:48 am

If the ECU thinks that there is low boost pressure because of a faulty MAP sensor (As ATX said a turbo engine cannot pull vacuum. Unless the turbo breaks) it simply injects a smaller amount of fuel. Conceivably it can run rich if a faulty MAP were to tell the ECU that the turbo was at full boost when it was not. Running rich in a diesel does not usually refer to a stoichiometric imbalance, but rather to the point where the engine makes a lot of black smoke.

bugnout · **Posted:** Thu Sep 25, 2008 12:08 pm

What did you soak it in? I use brake cleaner and only sprayed the sensor head part, not the body. Was worried that I would damage the seals or the housing.

dgeist · **Posted:** Thu Sep 25, 2008 2:24 pm

bugnout wrote:

What did you soak it in? I use brake cleaner and only sprayed the sensor head part, not the body. Was worried that I would damage the seals or the housing.

I've use MAF cleaner and B20, both with good results. I would think brake cleaner is a little harsh but it would probably still work alright.

jmoomaw · **Posted:** Thu Sep 25, 2008 3:00 pm

I used both brake cleaner and diesel fuel. Soaked it for a 30 minute intervals (used a small jar to only dip the sensor component). Used the toothbrush to scrub at it.

I was getting the same codes before and after cleaning the sensor. Just a bit faster after cleaning the sensor (PO299, PO401, PO107)

I haven't check the voltage per shop manual as yet. There are other problems with CAC Hoses and possibly a turbo boost valve that work intermittently. If I thump it when stuck it works fine for a few days until a cold or wet spell hits....but this thread is mainly about the MAP sensor.

Thanks for all the input...if there is more to know, I will keep watching.

Jim

PS...I clear the codes at AutoZone. They will let you borrow their Scan to read and get information on the codes. I just erased them and bought an air filter, oil and other items I will or do need as a thank you.

ATXKJ · **Posted:** Thu Sep 25, 2008 3:18 pm

Thump it and it works - sounds like a broken wire that's barely making contact - or a loose ground

bdptp73 · **Posted:** Thu Sep 25, 2008 8:25 pm

If you have P0401 and P0299 I would check the boost hoses for leaks/holes. Low voltage might be caused by boost pressure leaking out somewhere. These hoses are known for bursting. I know I am expecting mine to go out on me sometime.

jmoomaw · **Posted:** Fri Sep 26, 2008 1:56 pm

The input and output CAC hoses look good. They are black with orange linings which are understand are an upgrade form the 2005 stock hoses (Correct me if wrong) which make them newer than 74,000 miles and do not corrode with the oil deposits. The intake was oily at the CAC. I twisted it, look at all the spots that look like they could be leaks but the spots all rubbed away.

I next went to the PVC and could easily pull the hose off the puck (No Hose Clamp???...could this be the leak? It has a layer of oil that filled the rim. I am off to the autoparts store to pick up an elephant nose until my provent arrives. I assume this oil is the source of the oil in the inlet hose to the CAC...yuck.

There is also oil, wet oil around the 1st glow plug at the front of the engine!
Jim

dgeist · **Posted:** Fri Sep 26, 2008 2:41 pm

jmoomaw wrote:

The input and output CAC hoses look good. They are black with orange linings which are understand are an upgrade form the 2005 stock hoses (Correct me if wrong) which make them newer than 74,000 miles and do not corrode with the oil deposits. The intake was oily at the CAC. I twisted it, look at all the spots that look like they could be leaks but the spots all rubbed away.

I next went to the PVC and could easily pull the hose off the puck (No Hose Clamp???...could this be the leak? It has a layer of oil that filled the rim. I am off to the autoparts store to pick up an elephant nose until my provent arrives. I assume this oil is the source of the oil in the inlet hose to the CAC...yuck.

There is also oil, wet oil around the 1st glow plug at the front of the engine!
Jim

Not sure the hoses are new. Mine look like that and they are original, but if you've examined them and there are no splits, then you should be fine. As for the CCV hose, it would take an awfully strong venturi force to knock that guy off. Unless it's blown off now, chances are it's not your culprit, although a hose clamp wouldn't hurt (I added one when I added my provent).

Dan

bigugly · **Posted:** Fri Sep 26, 2008 10:39 pm

I purchased my CRD with just less than 10,000 miles. It had the CAC hoses that were black outside orange inside. The intercooler to intake hose burst at approx. 80,000 miles. I replaced both hoses to make sure the turbo to intercooler hose was not the next hose to go.

On inspection of the new hoses the Turbo to intercooler hose is different. It is black on the outside and inside and has about 3 layers of reinforcing cords. It also has the shiny wrapped look that the SAMCO hoses have. The intercooler to intake hose was just like the original black outside orange inside. I will make the assumption that the upgraded hose is the turbo to intercooler hose since it much different from original and I am glad I now have a provent since the intercooler to intake hose has not been upgraded.

jmoomaw · **Posted:** Sat Sep 27, 2008 6:38 am

feeling really lost here....
I have gone through the manual for a picture and name several times. I am thumping with the handle of a screw driver on a cone shaped silver component on top of the turbo. The CAC inlet lose comes out below it. It has a 1/4 in vacuum line entering it through a L-shaped connector. No clamp, just a real tight fit.

The vacuum line comes off a unit to the left that has several small vacuum lines coming off of it. This second unit has a cone shaped paper filter on the under side. The whole unit will easily slide off the bracket by lifting straight up.

What am I thumping on and what is the vacuum controller called so I can look them up....

Thanks.
Jim

ATXKJ · **Posted:** Sat Sep 27, 2008 9:05 am

I think it's the 'boost pressure actuator' controls the angle of the vanes in the turbo

jmoomaw · **Posted:** Sat Sep 27, 2008 10:05 am

Thanks,
I found it in the manual..No photos are diagrams to confirm. Looks like I need to check all small hoses as well. I will blow then out at work today with a light weight compressor (disconnected of course)
Jim

Each little thing gets me closer to clearing these da#@ codes!

gmctd · **Posted:** Sat Sep 27, 2008 1:40 pm

That code refers to the function of the device, usually not it's function in the system - invariably, it is resulted from MAP sensor failure, not lack of Boost - put a cheap 19.95 jcwhitney.com 30"vac\20psia Boost guage on it for verification

- sluggish response, not able to easily make 15psi = system problems

- 15psi + low voltage DTC = MAP failure.

jmoomaw · **Posted:** Sun Sep 28, 2008 9:15 am

I get intermittent sluggish response..The vacuum gauge looks like a necessary addition to my tools kit..

Now...here is a definitely newbie question...which hose do I unplug and plug the gauge into....I looked through the manual on the Turbo Charger and it does not mention a way to test the vacuum. Only a procedure to test for leaks using a pressure regulated charging tool that smokes the system.

If I remove the L connection on top on the Turbo Charger and plug in the vacuum gauge there...will that give me the reading I need.

jmoomaw · **Posted:** Sun Sep 28, 2008 9:17 am

I get intermittent sluggish response..The vacuum gauge looks like a necessary addition to my tools kit..

Now...here is a definitely newbie question...which hose do I unplug and plug the gauge into....I looked through the manual on the Turbo Charger and it does not mention a way to test the vacuum. Only a procedure to test for leaks using a pressure regulated charging tool that smokes the system.

If I remove the L connection hose to the top off the Turbo Charger and plug in the vacuum gauge there...will that give me the reading I need?

MAP Sensor Voltage Low

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