Why won't this VIN Write????

08 Dodge Sprinter 3.0 diesel No crank new ECM

I first got this call to program an ECM on this Sprinter which happened to be owned by one of our local Snap On dealers. It had a new PCM from the dealer. The PCM had been replaced because of a no start condition. I performed the programming and had no issues until I got to the VIN write procedure. On this vehicle the VIN must be written in order for it to crank which must be done with the Micropod II or capable scan tool. Under the misc. functions in WiTech II there are two options for VIN rewrite (the Mercedes/Chrysler software is strange) when you click on one option the tool says that it is unsupported. The other VIN rewrite option gives me an error code. process​.​filestackapi​.​com/resize=h:1000… process​.​filestackapi​.​com/resize=h:1000… The old ECM had no communication and smelled burnt So I was under the impression that I was battling a failing replacement PCM or a scan tool/software issue.

I also had 4 codes in the new module. process​.​filestackapi​.​com/resize=h:1000… 2100 Electric fuel pump (fuel level sensor) 2199 Measure unit (Fuel quantity control for high pressure pump) 2502 Fuel pressure regulating valve (boost pressure regulator short to ground) 3069 undefined Notice that the DTC description for the 2502 code reads “fuel pressure regulating valve” however the service information describes a fault in the boost pressure regulator. process​.​filestackapi​.​com/resize=h:1000… The code 2100 which is shown as “electric fuel pump” is really a code for the fuel level sensor. process​.​filestackapi​.​com/resize=h:1000… I guess prior to owning any OEM scan tools I imagined how nice it would be to have OEM tools and service info where everything is correct but in this case I might as well have been reading a poorly translated Chinese takeout menu. I assume this is because the information is taken from Mercedes and adapted to be used on the WiTech platform and is probably the reason why there are two vin rewrite procedures.

I also noticed the radio had no communication and would turn on and off randomly as well. I told them that whatever had likely caused the old ECM to fail is likely related to these codes, billed them for the programming, and told them if they needed help with the diagnostic to schedule some time and took off for my next call.

About a month later I get the call that they have been through everything on this truck and cannot figure it out. Although I’m dreading working on this Dodge/Mercedes I head out there to take a look at it. It had the same symptom, will not let me program vin, no crank and same 4 codes. process​.​filestackapi​.​com/resize=h:1000…

I really didn’t have much of a direction so I started by reading into the codes one by one. There is no description whatsoever in Techauthority for the 3069 code and the boost pressure regulator seemed like the easiest code to begin diagnosing. I did a quick check of the power supplied from the ASD and ground circuits which were both good. process​.​filestackapi​.​com/resize=h:1000… The signal circuit did not have any continuity to ground and when unplugged and the same code would set. Searching for a list of potential codes I found code 2500 which is a circuit open code. process​.​filestackapi​.​com/resize=h:1000… My assumption is that the circuit open code should set if the regulator was unplugged and since I had verified the wiring was not shorted to ground.

I was thinking the issue was likely internal to the PCM. I researched powers and grounds for the module. process​.​filestackapi​.​com/resize=h:1000… I typically do my powers and grounds checks with a sealed beam headlight. If the circuits can handle enough power to brightly illuminate a sealed beam than they should be able to power a module. For the purpose of this case study I used a test light. With key on should have healthy power at pins 1, 5, and 7, as well as healthy ground at pins 2, 4, and 6. I found power at 5 and 7 but no power at the black/grey wire on pin 1 of the ECM. process​.​filestackapi​.​com/resize=h:1000… That power comes from fuse 16 which I found missing from under dash relay block causing missing power. process​.​filestackapi​.​com/resize=h:1000… When the fuse is replaced all ECM codes clear and do not return. I attempted to rewrite vin number multiple times but still received an error and could not get vehicle to start. process​.​filestackapi​.​com/resize=h:1000… I assumed we had likely caused damage to the replacement PCM when attempting to program it with one missing power. Since the shop had purchased the module from the dealership they decided to tow it there to see if they would warranty the unit. Once a new PCM was installed and programmed the vehicle started and ran great with no codes returning. process​.​filestackapi​.​com/resize=h:1000…

Since then I have found a module reset procedure within the guided diagnostics in WiTech II. I have used this function to recover modules that have had programing failures and I wonder if it would have allowed me to fix this Sprinter without replacing then PCM. The interesting thing about this is that the module had consistent communication with one power missing and I was able to program it and look at the data stream without any issues. I would have never expected this bizarre concern to be caused by a missing power and was really only led to that conclusion because I never recommend replacing a module without checking powers and grounds.