My fellow R51 Brothers and Sisters,

My lovely wife was driving our Patty down the road and all of a sudden the power cut out on her. She wasn't able to accelerate but the engine was still on, the speedo and tac needles were bouncing up and down, and the electrical was for the most part dead. Luckily she was able to get off the road and when she turned off the engine, she wasn't able to get it started again, in fact, it wouldn't even engage the starter. When I got to her, I tried to turn on the hazards but got nothing. All electric gonzo! I disconnected and reconnected the battery of only two months old, was able to get some electrical back, turned the hazards on. I tried to start the engine but it killed electrical to the hazards and the guage needles started to bounce again. Even when the key was in the on position, I couldn't move the gear selector. I disconnected and reconnected the battery again and was able to get into neutral to tow to the shop. Completely at a loss with what this could be.
Just heard back from the shop that they think it is a bad ECM module and will cost a couple thousand to replace. This sounds like they weren't able to fully diagnose the issue and going with something that could be a definite fix even though it may not be the root cause...these guys aren't shady but there's still that voice in the back of my head.

Few things:
- WHen I replaced the battery, the positive terminal was completely caked in corrosion so naturally I cleaned it off when installing the new battery. When I opened the hood to disconnect the battery, the positive terminal was completely caked in corrosion again...weird
- We recently tried to have a bluetooth unit installed but with the lack of a dedicated AUX button, the unit I wanted did not work. Could the wiring they were messing with had a negative impact on the ECM?

Anyone have experience with bad ECMs? similar symptoms? Anything helps. This is my favourite vehicle and it pains me that it is in bad shape.

Many thanks!

Kel

R51's are absolutely infamous for corroded positive terminals blowing up ECM's. It's a real estate thing, location-location-location. The power path from battery to ECM on an R51 is 18" of straight-line wire without even a loop to protect against EMF traveling through the conductors. Get a big enough spark at the battery, the several thousand volt transients melt the protection diodes in the ECM and the party's over. I've replaced dozens over the years. Frontiers and Xterras with the same layout also have the same tendency.

A bad alternator/voltage regulator that is overcharging the battery will cause lots of corrosion on the positive battery terminal to build up. If you had just recently cleaned it off well and it built back up quickly on that new battery, I would be looking at the alternator first. The ECM may of gotten wacked is the process of overcharging the battery, if that's what happened. Hard to say what is possible with wiring in that attempt to install Bluetooth.

VStar650CL wrote: ↑

Tue May 16, 2023 8:08 pm

R51's are absolutely infamous for corroded positive terminals blowing up ECM's.

I would never thought ... That's just sad.

Thank you for your responses

Just heard back from the shop and they are asking for $3,500 for a replacement ECM and a reprogram. $2232 for the ECM, $250 for the program and $634 for labor, Diag is $80...and I am getting charged a Convenience Fee of $125??

Anyway, no root cause of the problem discovered so it could be another ticking time bomb waiting to go off.

Is this something I am kind of at the mercy of the shop or is it possible to get a programmed ECM? The install looks fairly simple

The ECM's are a complete PITA to get at, so they're probably charging extra labor. But yes, there will be used ECM's all over eBay with right or near-right programs. The problem on an R51 Pathy is getting at the part number tag to see the Hitachi part number, that has to match. It will be, for example, AAA??-??? where the A's will be letters and the question marks will be numbers, those all need to be identical. There will be other numbers but those don't need to match. You usually need to use a prybar and a mirror to see the tag on an R51, the ECM is wedged in right beside the underhood fuse and relay box.