P0341..Rough Idle...Smooths Out...Lose Tach

[Frog]

Ok. So, my ECM must be interpreting the voltage incorrectly, but, I’m not getting an APPS voltage high fault.

 

I’d attach a video but it’s only allowing me to upload 14MB.

 

My voltage is .483 at idle and 3.8VDC at full throttle. Not sure where the 160.5-160.8 volts is coming from.

[Great work!]

Just curious have you done APPS calibration procedure? Then do a stare and compare of the scans and live data. There could be some gain/ Offset values saved in the ECM.

[Mopar1973Man]

Just like the MAP sensor is misreported because not all live data tools do the proper math to display the values. Like most live data tools show 28.9 PSI value at idle when I know its actually ZERO boost.

[dripley]

The funny thing on mine while I was MAP sensor problems was 28+ at idle and then when the sensor let go 14.6 psi. That number sound familiar? never had it happen in in a higher altitude to see what it would say when they failed. 

[Mopar1973Man]

No different when I do a WOT run to 100 MPH the Quadzilla report my MAX boost at 69 PSI while I watch the boost gauge (ISSPro EV2) only show 49 PSI. Then watching the live data on the MAP sensor it goes up to 37.7 PSIa displayed but that was way back at like 12 PSI of boost. Again the math to show the sensor correctly is not present in the live data tool. Then any accuracy is lost above about 25 PSI. Everything above that is a gamble. The only thing that is dead on accurate is my ISSPro EV2 gauge.

Edited March 11, 2021 by Mopar1973Man

[dripley]

I am runjing off of an EV1 and it seems tomfunction just fine also.

[Mopar1973Man]

18 minutes ago, dripley said:

I am runjing off of an EV1 and it seems tomfunction just fine also.

Just comparing live data & Quadzilla data vs. Actual boost gauge. @Frog This is why you might report strange voltage from the APPS sensor. Again math issues of the data given to the live data tool and raw data is given.

[dripley]

On 3/8/2021 at 8:54 PM, Frog said:

Ok. So, my ECM must be interpreting the voltage incorrectly, but, I’m not getting an APPS voltage high fault.

 

I’d attach a video but it’s only allowing me to upload 14MB.

 

My voltage is .483 at idle and 3.8VDC at full throttle. Not sure where the 160.5-160.8 volts is coming from.

I believe what Mike is saying is the live data tool is not able to read the voltage properly. Just like my scan gauge cannot read the MAP sensor properly. It is just a glitch and the ECM is not seeing that crazy high voltage.

[Frog]

Thanks, for all the input. Quick question....if yall connect with a decent scan tool, will it differentiate between the PCM and ECM?

 

So, here is something I tried. Since I had a sneaky suspicion that my engine ECM was incorrect, I purchased a used one and found out that mine in-fact had the wrong ECM. It was for a 2001 not a 1999. I disconnected the PCM and then tried to connect with my scanner. During auto scan it pulled up the PCM and TCM...why TCM, I have no idea. So, of course I was getting a P1698 no CCD from PCM...which is expected. But the TCM, shows all my engine readings. I can even perform some active tests.....grid heaters, wait to start light and fuel pump. My scanner will cycle these functions on and off for approximately 4 seconds on and 2 seconds off. If I review live data then it is the same as before, high APPS voltage weird temps.

 

So, I tired it the other way...disconnected the ECM and connected the PCM...of course it just pulled up the PCM. Now, the really odd thing is that when I would try to access the information on the selected control module, then it would just give me a hex a decimal location. With the ECM disconnected, it actually shows me the info...software, truck arrangement (2wd,4wd), year, make and VIN...all from the PCM. Well, this PCM is not from my truck cause the VIN does not match. But it does say it is a medium/light duty manual. 

 

Well, my next step was to connect the old 2001 ECM to see what it will do. When the scan tool auto connects it only pulls up the PCM. Under the PCM are all my active tests for the engine. No other ECM will come up....I have a pass thru that will detect the ABS, BCM, Anti Theft etc...I just didn't want to hook it up cause auto connect takes 10-15minutes. When I check live data, it shows the APPS voltage @ .488 and Position @ 0% as I depress the pedal the % goes up along with the voltage...voltage maxes out at 3.8VDC and I verified this at the APPS connector also. At this voltage the APPS is showing 100% So, am I going crazy or what? I called Autel and I have to call back tomorrow when I have more time to let them remote in to the scanner to see if a setting or protocol is missing or messed up.

 

Should I be able to see two separate computers...PCM and ECM??

 

Thanks again.

On 3/9/2021 at 8:53 AM, Great work! said:

Just curious have you done APPS calibration procedure? Then do a stare and compare of the scans and live data. There could be some gain/ Offset values saved in the ECM.

Yes sir, no change. 

Info from the PCM. I cannot access this if the ECM is connected.

This is all I get with the ECM connected.

Edited March 12, 2021 by Frog

[Mopar1973Man]

That is correct... The PCM is the primary computer with the most information. It holds all the info about the truck and options. 

 

The ECM is a secondary computer and relies the PCM for complete info.

 

The PCM is the starter of the CCD Network and the instrument cluster is the Bias Voltage module to get the CCD bus set up. Without the PCM there is no way to tell the ECM that road speed is over 20 MPH turn off the grid heaters. Again like the ASD relay that shuts down the engine if way out of range. That is also controlled by the PCM. Keep in mind the Cummins ECM is NOT OBDII compliant. Look up PID 1C and check out what it reports. Hex 05 which states the ECM is not OBDII compliant. Weird but true.