Hi, this maybe slightly long post.
I have a Captiva 13 sport 160k+ odm. It runs good to excellent. Smooth engine and transmission etc...
When I hook code reader and try to run tcm check, the reader can't detect tcm!
When checking other modules they return lost connections codes. Those codes return after erase and rescan.
U2105 ebcm to ecm
U2106 ebcm to tcm
U0100 pbcm to ecm
How to diagnose if it's connection or module problem?
More details:
when I got the car it had voltage stability problem; either drop low until car shake or jump high until different modules fault for a second. I added thicker ground wire from battery to body and engine to body as well as replaced current sensor. That fixed voltage fluctuation. Internet was more helpful than dealer and it looks to be common problem with this car model.
In one situation, after I did gdi cleaning (bg injector cleaner) I removed ecm tcm and other module fuses for few minutes to reset memory then took the car for soft drive (15-20 minutes). I kept scanner connected to monitor LTFT rate (it was -25 or more before gdi cleaning; less than -10 after). Suddenly the dash, scanner and transmission froze. Speedometer stuck, transmission stayed at the same gear before everything froze. Restarting car didn't fix it, but removed ecm fuse then return it and all fixed. I did all modules scan and scanner was able to find tcm and connect to it. After I erased all codes scanner cant reconnect to tcm like before.
Side question: the car had been running at lean condition for some time. After I did fuel system (bg 44k) + gdi (bg gdi cleaner) + air intake (bg 261) the lean issue seems to be resolved. However, I get P0420 catalyst convert low efficiency. I have not checked any sensor yet, but if sensors are ok how to determine if converter is irreversibly damaged? I have 2 extra BG 44k I'm planning to use perhaps it resolved the converter efficiency.
What scan tool are you using? You're going to to need a bi-directional scanner for a diagnosis that serious.
I will receive xtool d8 soon (tomorrow or a day after).
Now I only have Innova regular scanner (not bi-directional)
Probably D8 will make it easier; given all reviews. But I'd like professional thought to help me cruise diagnosing.
If you up for challenge, how to diagnose with little to cheap resources?
if the modules aren't reachable then a scanner will get you nowhere
How to diagnose if it's connection or module problem?
Obtain electrical schematics and connector end views for each unit from service information.
Locate power, ground and serial bus pins.
Verify presence of correct voltages and ground continuity with multimeter and probe set.
Verify presence of serial connection.
That's all and end user can do.
Absence of these means the problem is external to module.
If everything checks out, then your only option is the replace the module.
