Hi everyone, I'm the new owner of an '90 Civic Si and find the car to be a joy to drive but I have a few problems. First off, whenever i rev over 5.5-6k (in gear or not) the battery light goes on and stay on until the rpm drops around 4.5-5k. Now i get two codes from the ECU (4 & 9), respectively the TDC and 1st piston position sensors.
I think both problems are related, but the ECU codes point in the direction of a faulty distributor, while the battery light leans towards the alternator. The car always runs fine, like there's no problem at all...
Any thoughts?
Thanks in advance

 

Yes, the 4 and 9 would indicate a distributor problem. Take the cap off and check for red dust. If there's a lot of it, it could be a sign of a failing distributor bearing. The dust may be interfering with the sensors.

Just a guess about the battery light. Maybe reving makes the worn out brushes skip enough to reduce the output and trigger the light?