trans slips on highway downshift with SES light
I have a friend'* 1995 SSEi while he is out of town to replace the supercharger coupler. While I'm working on it, I'd like to see if I can help repair (or at least diagnose) a few other little problems.
The SES light comes on after running for about a minute. Engine has no hesitation but I seem to remember it having a bit more power when I drove it last year (could just be the trans feeling more sloppy). The transmission shifts very smooth, but when at WOT, it doensn't downshift, it just falls into neutral and the engine winds up to the rev limiter, or falls back into overdrive when I let off. (I only did that once on the highway)
I dont have a code scanner at my disposal right now but he said he checked it and it was setting a P0640 or a P1640, I'm not familiar with OBDI nomenclature. Could the trans problem be causing an SES light, or is it just worn and most likely unrelated? The car has 131,000 miles and has been very well maintained.