Fan clutch / MAP sensor questions

[Oil Stain]

Have 2012 3500 Longhorn about 97,000 miles and deleted. I'm using MM3 tuner. My fan clutch is pretty much matching my rpm's while driving around town. Fan clutch was replaced about 2 years ago.

My thought process and troubleshooting is telling me that the PCM is seeing a high temp somewhere and is commanding more fan speed. Now hold that thought.

In the MM3 I found a PID called "Intercooler outlet temp" The reading I'm getting is around 180-230F degrees.
Upon researching, it seems to be the MAP sensor. I unplug it and the reading pegs at 392F and when I reconnect it, goes back down to 180-230F.

It's cold here today and before starting motor with just the key on and sensor removed and still connected, I was reading 151F. And it is 50F outside.

So here is my question, does this sensor heat up to read air pressure like a MAF sensor? Or should it read the actual temps going through the intake plenum?

 

[Oil Stain]

Yesterday, replaced the MAP sensor (wasn't cheap) and still seeing high temp readings. Does anybody know how this temp portion is supposed to work?

 

[Tuesdak]

I would look at fan PWM% commanded, FAN RPM, AC pressure, and ECT. I don't recall if there is a 'fan desired RPM' offhand.

Note the fan is "overdrive" and can run higher than engine RPM at full lockup.

I would suspect the MM3 may not be reading and displaying the correct temp for whatever bug.

Bottom line if the PWM% is "0" and the fan is roaring there is a problem with say a short keeping the clutch signal "on" or fan clutch seizing up.

"15% PWM" appears to be "maintain fan RPM" from the ECM. If you see this or higher with fan roaring, then yes, something is telling the ECM hot: need fan on. (Maybe short or other problem.)

Give the fan 2 min at 1200 or more ENGINE RPM to change RPM on/off.

Example of PID's here:

https://www.turbodieselregister.com...thermal-dispersant-on-an-ac-condenser.264486/

 

[Oil Stain]

I would look at fan PWM% commanded, FAN RPM, AC pressure, and ECT. I don't recall if there is a 'fan desired RPM' offhand.

Note the fan is "overdrive" and can run higher than engine RPM at full lockup.

I would suspect the MM3 may not be reading and displaying the correct temp for whatever bug.

Bottom line if the PWM% is "0" and the fan is roaring there is a problem with say a short keeping the clutch signal "on" or fan clutch seizing up.

"15% PWM" appears to be "maintain fan RPM" from the ECM. If you see this or higher with fan roaring, then yes, something is telling the ECM hot: need fan on. (Maybe short or other problem.)

Give the fan 2 min at 1200 or more ENGINE RPM to change RPM on/off.

Example of PID's here:

https://www.turbodieselregister.com...thermal-dispersant-on-an-ac-condenser.264486/

Thanks for answering. I went through all of the PID's and could not find fan PWM% commanded, or AC pressure. I will need another scan tool which I do not have on me at the moment. At home I have the OBD Link M+ with the AlfaOBD software, that should tell me, I hope.

All I know right now is the MAP sensor located in the intake should read ambient temp when sensor is pulled out of the intake, is my thinking. This is before starting the truck for the first time. I'm seeing at least double or more temp degrees. That is my thinking, but would also like to see the parameters that you mentioned as well.

 

[AH64ID]

There isn’t a sensor for intercooler outlet temp, it’s just an algorithm. I wouldn’t put any stock in that temp reading.

If a sensor is suspect I would put AAT, IAT, and ECT on the MM3. Then look at them after sitting overnight. They should all be about the same.

 

[Oil Stain]

There isn’t a sensor for intercooler outlet temp, it’s just an algorithm. I wouldn’t put any stock in that temp reading.

Here is the part number for the new sensor I installed using my VIN at the dealer. 68282012AA -
Dodge Cummins Sensor - Manifold Absolute Pressure Sensor - MAP Sensor - Air Intake Pressure Sensor

When I unplug it the PID goes to 392F degrees. Also if I run the truck with it unplugged, I will get 3 error codes. I didn't right them down, but the 3rd code says that fan is set to high RPM's. This is what has led me to think that this high temp reading on PID "intercooler outlet temp" is my issue.

 

[Oil Stain]

If a sensor is suspect I would put AAT, IAT, and ECT on the MM3. Then look at them after sitting overnight. They should all be about the same.

Here's my MM3 that you asked for.

 

[AH64ID]

What was the outside temp?

The trans being cold and the AAT being hot could be normal if it got cold overnight and now the truck is in the sun.

The IC-OT is calculated, don't worry about it.

The sensor you listed is the one providing the IAT temp on your MM3.

 

[Oil Stain]

What was the outside temp? High 50's

The trans being cold and the AAT being hot could be normal if it got cold overnight and now the truck is in the sun. Correct.

The IC-OT is calculated, don't worry about it. Ok, but what about the codes it through saying fan running at high speed?

The sensor you listed is the one providing the IAT temp on your MM3. I will have to disagree because see photo below.

Below is the sensor I'm dealing with on the side of the intake.

Below is what I see when I unplug that sensor. The IAT didn't change, but the IC-OT. I'm so confused...

Below photo is before I unplug anything.

 

[AH64ID]

Interesting, I would have expected the IAT temp to do that not the IC-OT. Maybe the labeling is different on that year for the MM3.

If you're getting the same reading with both sensors then I would suspect a wiring issue.

It does also appear that your fan issue is caused by that high temp reading.

 

[Oil Stain]

Interesting, I would have expected the IAT temp to do that not the IC-OT. Maybe the labeling is different on that year for the MM3.

If you're getting the same reading with both sensors then I would suspect a wiring issue.

It does also appear that your fan issue is caused by that high temp reading.

I agree with the high temp issue. I want to know why that one sensor is reading so high in the first place. Can anyone else see what there getting on their truck?

Unless anyone else can share their input, when I return home, I'm going to try my Min Maxx tuner when I first bought the truck new and see what happens.

I'm leaning on the PCM software may be corrupt. I at one point had the Mini Maxx, then EF Live and now MM3. If I remember, something happened to the program with the EF Live. They sent the tune for a 2011 instead of a 2012. Thats when things started to get a little weird. Same thing happened with the first vendor for MM3 and had to try another vendor.

I may go to the dealer and have them reflash the PCM to the latest software and go from there.

 

[AH64ID]

Did this start when you installed the MM3 tune?

 

[lpennock]

Looking at your displays, IAT is probably Inlet Air Temperature (the one on the air filter), rather than Intake Air Temperature. IC-OT is the Intake Air Temp (Map sensor) if it jumps up with grid heater you know for sure.

 

[Oil Stain]

Did this start when you installed the MM3 tune?

It's gotten worse over time.

 

[Oil Stain]

Looking at your displays, IAT is probably Inlet Air Temperature (the one on the air filter), rather than Intake Air Temperature. IC-OT is the Intake Air Temp (Map sensor) if it jumps up with grid heater you know for sure.

You are correct! But again, why is it reading so high before I even start the truck. I had the sensor out of the intake, yet still connected because I didn't want the grid heater to give a false reading. You can see in the photo, not even started the truck and no grid heater, I'm reading 174.99F how is that possible? My old sensor and this new one have been close +/- 20F. Again, still reading high.

Without a better scan tool, this is all I got to go on. Sucks...

 

[Oil Stain]

History on the fan clutch. Brought truck brand new in '12. Now have 97,200 miles. Had fan clutch issue not turning on when remote started. This started around 6-7 years ago. Went to Colorado from Florida truck started to over heat past 220F and no fan. That was EF Live. About 3 years ago, I ordered a new fan clutch with the part number ending in AB. My original was AA.

I installed it and the fan clutch would never disengage. Returned for another one. The second one worked but would not disengage until truck warmed up. But it at least would go down to low speed, during normal driving. I think at this point I had the MM3.

As time went on, the fan clutch would get worse. Meaning the time it took to return to normal speed was taking longer. And now it's the worse it's even been. It will not return to normal only when I'm in top gear and RPM is 2k+ and doing 80MPH.

The following is from Cummin's on the operation of the fan clutch on what it needs to do its thing. There's more, but only pasted this small part.

Feature / Parameter Range Default

Fan Control Fan Type - Parameter ON/OFF, HIGH/LOW/OFF, or Variable speed ON/OFF

Fan Control Drive Ratio - Parameter 0.1 - 20 1.19

Fan Control Maximum Fan Speed - Parameter 0 - 4500 rpm 2500 rpm

Fan Control Air Conditioner Pressure Switch - Feature Option Enable/Disable Enable

Fan Control Air Conditioner Timer - Parameter 0 - 3600 seconds 30 seconds

Fan Control Air Conditioner Vehicle Speed Control Feature - Feature Option Enable/Disable Disable

Fan Control Fan On During Engine Braking - Feature Option Enable/Disable Enable


Theory of Operation

In order to meet the cooling needs of several vehicle and engine subsystems, OEM's (Original Equipment Manufacturers), often install an engine driven cooling fan which can have a considerable impact on the performance and operation of the ISX engine. The ISX Fan Control feature is designed to minimize the fan's impact on the engine, thereby promoting higher engine performance, increased fuel economy and greater durability.

 

[Oil Stain]

Bottom line if the PWM% is "0" and the fan is roaring there is a problem with say a short keeping the clutch signal "on" or fan clutch seizing up.

"15% PWM" appears to be "maintain fan RPM" from the ECM. If you see this or higher with fan roaring, then yes, something is telling the ECM hot: need fan on. (Maybe short or other problem.)

Give the fan 2 min at 1200 or more ENGINE RPM to change RPM on/off.

Example of PID's here:

https://www.turbodieselregister.com...thermal-dispersant-on-an-ac-condenser.264486/

I was able to monitor the PWM. It was at "0". When should I see it change? I had the truck running and in park and was giving it RPM's and it just stayed at "0".

The fan is not locked in to a full RPM. It does vary. Say I'm doing 40 MPH, I can watch the fan RPM drop from say 1500 down to 1300 and quickly go back up again. Driving around town is where the fan is say 300-500 RPM lower than engine RPM.

Once I go on the highway it will be at 1050-1160 RPM and the engine is turning 2100 RPM. Once I get off highway, it seems to be ok staying around 1200 RPM. If I turn the truck off and on again, the craziness starts all over again.

 

[Oil Stain]

Got a 1 day access to Tech Authority, went through what I could find on the fan clutch. Got wiring diagrams. Could not find a step by step troubleshooting. Only how to test to see if fan will run by applying 12v to the fan connector. Well I know the works without this test.
Got a hold of my OBDLINK M+ and AlfaOBD software. Did not see any hidden codes. Tried to run a test on the PWM% for fan. With engine running at operating temp, the test came back saying "could not run test due to parameters not being met". Ok, what parameters. If I turn engine off, but key on, the test will run. Not sure what it is doing, I don't hear anything.

I hate that I have to take it to the dealer, but would like to fix myself. HELP....... please.

 

[AH64ID]

I really don't think the issue has anything to do with the fan clutch.

 

[Oil Stain]

I really don't think the issue has anything to do with the fan clutch.

I agree.