No communication with PCM after minor autobody work
Hi Everyone,
I was called into an autobody shop for a 2017 Mazda CX-3 2.0 SkyActiv no start. They claimed that the only work done to the vehicle was replacing the left head light and a small metal bracket that contains two grounding points (one of which holds the grounds for the PCM). Upon scanning the vehicle, I was unable to communicate with the PCM. I scanned the other modules and they all had codes pointing to no communication with the PCM. I checked the grounding bracket to see that the grounds had proper contact (using LoadPro), and even by-passed them with a jumper wire just to make sure.
I tested ground, positive, and CAN signals at the PCM and everything checked out. Everything pointed to a bad PCM. It's strange, as they claimed that they only disconnected and reconnected the grounds (no welding, no boosting, no arcing marks on battery posts, etc.).
The shop called the dealer and was quoted $1000CAD and a one week lead on a new PCM. I searched on car-part and a local yard has a used PCM with the exact same part number, which I will pick up on Monday.
My question is: Has anyone successfully coded a used PCM module for a 17 CX-3 (Denso PS2218881A)? Is it just a VIN change or is there security programming required? Can it be done with pass-through / a key programmer or is cloning the only way? In the past, I coded used Mazda PCMs and security with my Ford J2534 subscription. Is this still the way or has it change?
Thanks!
First of all check out this tsb/position statement. Make sure the CORRECT ground bolt is used and grind all the paint off. rts.i-car.com/images/pdf/oem….pdf it may very well have cooked the pcm if it ran much with those grounds off. Toyota is bad about the same thing. as far as programming, you will need theft access which requires a mazda incode and…
I believe a key programmer tool will bypass the incode and outcode on many Mazda models depending on the tool being used and “the day of the week” :l
While I have not tried to do a used pcm on a newer Mazda I would be very surprised if this is even possible. The days of putting in used modules are gone. Most every manufacturer is making these things one time use only. I'm curious to see what you find. If nothing else at least you can just install it and see if you have communication. Then it'll make you feel better about spending a grand on a…
Thank you so much for your insightful response. Everyone's diagnostics should be doubted unless they've proven otherwise, especially mine. Unfortunately I was not familiar with voltage drop testing. I've read an article and watched a few videos since. Everything you said makes sense in this case. I tested the CAN signals and positive with the ignition on, but not the grounds. I only did a…
Ideal would be 0 volts but anything under 0.5v under a load should be good
Good morning Christopher, I hope a few thoughts help you as you continue on. Resistance testing has its uses, but they are limited. One intact strand of wire is all it takes to pass a resistance test. That one strand of wire isn't going to spin the starter for you though. Voltage drop testing allows you to examine circuit operation as designed and operating (or failing to operate). For…
Do a voltage drop test on the pcm power and grounds with the key on and back probed at the connector for the pcm… should be 0 volts
Mazda programming will not work with Ford Fjds. For this vehicle you would use MMP available from MazdaServiceInfo.com It is very similar to Ford’s software but is definitely different. I have successfully programmed several used Mazda PCM’s but I am unsure if a 2017 will completely program correctl. If you do perform this programming I would recommend leaving the pcm disconnected…
From my understanding, anything above 2010 needs LSID to do parameter reset. Programming keys only, sometimes won’t work on newer models. I would be prepared with ur LSID info just to be safe. PMI should work if you don’t need the latest calibrations, if the original PCM hasn’t been updated recently.
Chris, I curious to see if there was a resolution to this problem. I have a 2018 CX 5 with a similar problem. Car drove into shop when on frame machine for minor pull and left side apron section. Once back together it will crank but won't start. Read codes found implausible signal from PCM to all other modules. Once cleared have codes for Electronic valve timing control circuit. I clean all…
I just left the autobody shop. They said that the bracket came with a grounding bolt and a sticker to prevent painting the said area. With battery and PCM connected, did a voltage drop test on each bolt both to PCM body and to shared ground inputs. All were around 50mV and case was around 50mv climbing to a max of 150mV at times. Headlights / high beams work normal (grounded off same bracket)…
Chris, After retracing my steps found blown 15 amp fuse. Fuse appeared good but once I checked it with an ohm meter I realized it was bad. I believe it is labeled Eng2 in the main fuse box. Sometimes I'm just going too fast to find the obvious… Good luck Chris keep us posted
Update: I received and plugged in a used module, and still no response from PCM. I'm unable to scan it and all other modules on the network throw codes for PCM communication. I re-traced all my trouble shooting again. The module receives 12v and grounds. I did a drop voltage test by back probing the PCM with the ignition on and get no more than 50mV drop. Tried loading the circuit with with my…
Drumroll please…. Engine Fuse 2. I had to walk out of the shop with my tail between my legs. This was a perfect storm of rushing through the basic checks, jumping to conclusions (based on customer leads/suspicions), confusing wiring diagrams, and overcomplicating things with my brand-new, fancy tools ie. oscilloscope, LoadPro, ect. I hadn't done any vehicle diagnostics for over 4 years as I've…
The AES test kit is fantastic. After seeing so many well know diag guys here and elsewhere recommending it, I picked one up a few months back. Pretty sure it comes out for every diagnostic job now. The only piece I don’t really like is the back probes. The sheath runs too close to the probe tip restricting how far you can easily probe into a connector. Otherwise A+. Also thank you for sharing…