p0112 and p0237 same time bad ecm??

[rgraham]

My son has a 2002 Ram 2500 HO 6 speed manual. About a week ago, the codes p0112 and p0237 showed up.We took off the Edge EZ otherwise the truck is stock.Cleaned the IAT sensor. Did not look that dirty.The MAC Scan tool (determinator) was unable to read the IAT or MAP voltages.Not sure if this is a limitation of the scan tool or an ECM problem.We cleared the codes but they return immediately when the ignition is on. We checked all the grounds and cleaned the battery terminals.The batteries were both at 12.7 volts.Measured resistance from the IAT gnd terminal on the connecter to engine block and got 0-0.1 ohms.So I think the grounds are ok. Measured the voltage of the IAT signal return wire while running and it was 1.6 volts. (1.35 not running).So I think the IAT sensor is ok. We did step 4 of the p0112 error code trouble shooting. 4. Using DVOM, measure resistance between IAT sensor harness connector terminals. If resistance is less than 100 ohms, repair short to sensor ground in IAT sensor signal circuit. If resistance is 100 ohms or greater, replace and program the ECM. See appropriate REMOVAL, OVERHAUL & INSTALLATION article.We got 6.8 kOhms. We removed the ECM and measured the resistance between pins 7 and 11 and got the same value. So we think the ECM is bad.Is there any other DVOM tests that can be done to ECM to determine if it is bad?Can Cummins test an ECM on the bench (removed from truck)?If it is the ECM, where is a good place to get another one?

[Mopar1973Man]

I would try replacing the IAT and MAP sensors first before the ECM... Also check the driver side ground on the battery since this is the main ground for the ECM. Maybe a weak connector? Typically when a ECM goes all sensors show a hi volt or low volt code...

[rgraham]

The IAT sensor seems ok. Can a failed MAP sensor cause the ECM to report a low voltage on the IAT? We poked a straight pin into the signal wire on the IAT and measured the voltage while running.The voltage was 1.35 with engine not running and 1.6 to 1.7 idling.So we assumed that the sensor is working correctly. We measured the resistance from the IAT gnd to negative terminal on the driver battery and got virtually 0 ohms. Is this an adequate check? We have access to a shop (heated) on Saturdays. Currently the truck is in the parking lot without the ECM. I work near the St. Paul MN Cummins service center. Can Cummins verify the ECM is good or not? I was going to take it there and ask.Based on the step 4 test and that it appears that the IAT is working, we assumed that the ECM is bad. The p0237 test involve using a scan tool to view the MAP voltage. Which scan tool should be able to do this? We used a Fancy Snap-on one (Verus?) with a LCD display. It showed 0 volts for Intake Air and Boost (assuming that is the MAP). But we were not sure if the data was real or the scanner can not read it.

[Mopar1973Man]

Like my little cheap SGII shows IAT and MAP signals... But my SGII mis-reports the MAP sensor as being like 28.3 PSIa (atomshpere). I really hate pointing the finger at the ECM so far the few I've talk to have no way to test ECM other that full replacement with a new ECM. But remember there is 46 different ECM's... Federal, California, 5 speed, 6 speed, automatic, etc... ECM's are not cheap...

[dripley]

I would try replacing the IAT and MAP sensors first before the ECM... Also check the driver side ground on the battery since this is the main ground for the ECM. Maybe a weak connector? Typically when a ECM goes all sensors show a hi volt or low volt code...

i would have to agree with mopar. when my ecm went out i got high and low voltage dtc,s form all of my sensors, temp gauge was all over the place just a crap load of stuff that happened all at once. the only people i saw who would test the ecm were a couple of rebuilders, dont remember who they were. you can search the internet and find them pretty easy. just to be honest i am not a genuis when it comes to the electronics on these trucks. i learned alot from these guys while dealing with my problems

[jlwelding]

Do not deal with ECM Outlet he is a scam artist he screwed me out of 555.00 about5 months ago. He is still in bussiness it looks like. If you type in ecm outlet you will see this number 1-248-289-6063 tell everyone you know. I called the cops and they know all about him, why they dont bust him I have no clue.Call and ask for Jeff and see what he says, he could be going by Jeff or some other. Sometimes his girl friend answers.

[rgraham]

Update Got new IAT and MAP sensor from Cummins.The new IAT sensor did not clear the P0112 code.The Map sensor was the wrong one. The one on the truck has a wider black connector and the one from cummins has a smaller gray connector. Was there a change in sensors? Cummins used the engine serial number to look up the parts.Going back to cummins to get the right sensor. Cleaned all the grounds. Checked all the wiring from the IAT and Map sensors to the ECM. No shorts or opens. So all the wiring is good. We did disconnected the coolant temp sensor to verify that the ECM would throw a code and that the scan tool could clear it. All that worked fine. We left the batteries disconnected over the weekend. Measured the voltage on them and they were both 12.6v. So the batteries seem good. We connected the new IAT sensor with the MAP sensor disconnected. Could not clear the IAT code.Would a bad or missing MAP sensor also throw a P0112 IAT low voltage code?What else could it be?

[Mopar1973Man]

P0112 is a short to ground on the +5V side which would show 0 Volts on the ECM... But a open lead or a sensor missing would be a P0113 where the line is un-grounded and would show +5V at the ECM. Hopefully that helps to find the issue... The only thing beyond that would be start calling around to see if a ECM rebuilder would be capable of bench testing a ECM but so far I've never seen one yet... Or another idea is to see if a Dodge dealer would hook up a DRBIII tool and check the ECM and sensor for you but you know the shop hour rate is steep...

[rgraham]

We measured the voltage on the IAT connector and it was 5 volts.So there is no short to ground. So the P0113 IAT sensor voltage high code should have been set. All the times we scaned and cleared codes, it has always been P0112 and P0237. The only other code we saw was the Coolant temp voltage high when we disconnected the coolant temp sensor. So it is looking like it is the ECM.Any recommedations on a ECM rebuilder? Or ones to avoid?