PCM no Com
Greetings, I'm back with another no crank… This time I verified 1st off that the starter is not the culprit! :) This customer called stating that after starting the vehicle it ran for a couple of seconds then died and would not turn over after that. Upon getting to the vehicle I verified that there was no crank, and diagnosing the starter relay found it had no control power. I verified the starter would turn over by jumping pin 87. Then testing starter fuse #2 in the driver's side junction block I found that it had no power! As shown in my diagram, from the Ignition switch there is power to the J/B pin D3 but nothing to fuse # 2! From there I finally connected my scan tool to check the computer for codes. That is when I found a no comm to the PCM. Also there is no MIL illumination at key on. Tomorrow I'm going to go back to the vehicle and diagnose the PCM further. The customer states that this is the 1st time this has happened and he only has one key. And the only modules that come up in the scanning of the system is the Engine and SRS. No Immobilizer or body control module or other system shown. ???
I appreciate any suggestions and direction that I can get from you more knowledgable technicians! Thank you, Doug.
I would not be concerned with the fuse lacking power yet. I would focus on Active PCM power and ground. Also check 5 volt reference and make sure you do not have a shorted sensor bringing the bus down.
Sounds easy enough jump power to fuse 2 (with key on )and see what you got ether an open between outside jb and ignition switch or possible ignition switch. Id give that all my attention first.
Just a heads up not uncommon for Toyota dash J/B to corrode prongs on relays & fuses here in the Midwest stuff even freezes in it like the IG1 relay .
I'm a little confused. You said that there's no communication to the PCM, but you also said that the Engine and SRS come up during a scan. Were you saying that there's a code U0100 in a module? I'm also not seeing pin 87. I'm guessing that you're talking about the output of a Bosch-style relay and mean pin 3 on the STA relay. There is a separate key transponder ECU and you should be able to…
I'm sorry about the confusion Paul. What showed up on the system scan I think it was Engine - ECTS ( I'm pretty sure that's what it said I don't have that information right now though) and the SRS. And then when I tried to communicate with the PCM module it didn't see it. Also yes pin 3 on the relay. There was power to pin 5 and ground on pin 1. My Launch didn't show an Immobilize module. I'm…
No worries. I spend a great deal of time confused, so I'm used to it :) On the CAN bus there's the ECM, ABS, yaw sensor, and the steering sensor, but I'm guessing that the yaw and steering won't appear as modules and will report data to the scan tool through the ABS. There's also a separate BEAN network with the Body, Back Door, and Theft Deterrent control units, but I didn't see any connection…
Right on! Sorry I couldn't get back to you sooner, I had another job to go to after this one a few miles away and got back after 8. I will be writing up a resolution tomorrow, but was finally able to communicate with the system ( this was with my Verus instead of the Launch ) and tried the key and the darn thing started up!! This was after I was having no success pin-pointing the problem and…
Yeah I'm sure it wasn't that Paul but I don't know if it was just hooking up the Verus but all of a sudden it was accepting communication. Right after I did my test To the computer I tried it and it was still no start then I came back with the virus and it hooked up and started, And still is good! Really don't like the fact that I have no clue what fixed it but I hope it stays fixed!
Actually the Immobilizer module was not showing when the no crank was there, only the Engine, ETCS, ABS and the SRS were.
Aside from power ground and communication, I have also seen the 5v reference shorted to power which will take out the computer. facebook.com/groups/3138381…
Thanks for that FB group link Jamie! Don't know what actually fixed it but really thankful that he didn't have to tow it away! Hopefully it will stay fixed. Time will tell.