I’ve learned a lesson about diagnosing strange problems. When doing electrical diagnosis you should always check fuses early on, but I’ve now learned that you should also check fuses if you have a strange problem, even if it doesn’t seem electrical.
My brother has a 2001 Honda CR-V and recently was in a minor rear-end accident. The body damage wasn’t that bad, but it seemed that somehow the transmission got damaged. It was flashing the D light in the instrument cluster and was in a failsafe mode, affecting driveability. Along with that, the speedometer wasn’t working. Then, when we picked it up from getting the body damage looked at, the alternator wasn’t working, which made no sense.
An issue I ran into while trying to diagnose the transmission problem was that my cheap code reader could only read engine codes, not transmission codes. Then I remembered that some older cars, like my 1997 Civic, have a “service check connector”, which is a two-pin connector under the dash. All you do is connect the two pins, turn the ignition on, and the check engine light, SRS light, and others will flash in patterns indicating trouble codes. It only gives you a 2 digit code, but Honda service information helps you correlate those codes to regular OBD-II codes. Sure enough, his car had one of these, right next to the OBD-II connector.
With a paperclip jumping the connector, the transmission D light flashed 16. That correlates to a P1768 code, which is for “Problem in A/T Clutch Pressure Control Solenoid Valve Circuit.” The clutch pressure control solenoid is also called the linear solenoid and is located on the front of the transmission, in an awkward spot that would make electrical testing hard. A new one would’ve cost about $170.
While that gave us somewhere to go towards diagnosing the transmission problem, there was still the issue of the alternator not working. However, with the service check connector jumped, not only was the transmission D light flashing, but the check engine light was flashing. The code it was flashing 20, which is a P1297 code, indicating a problem with the Electrical Load Detector, part of the alternator circuit.
My brother took it upon himself to dig through Honda service information as well as do some googling, and found some people having similar issues with their alternators. One example was someone who replaced their alternator and it still wasn’t working, and it turned out the fuse for the electrical load detector had blown. Knowing that, he went looking at fuses and found that Fuse 15 in the under-dash fuse box is listed to be part of the circuits for the alternator, speed sensor, gauge assembly, and engine/transmission management.
Sure enough, it was just a fuse. One single 7.5 amp fuse caused all the problems his car had. How it blew when he was rear ended we’re not sure, but everything’s working fine now so unless it happens again I am happy with it. Moral of the story, always check fuses when you have strange problems, even if they don’t seem to be electrical.
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