tyncobb

1994 Lexus LS400 had CEL and ABS light, was driving on highway at 65 and all of a sudden I had power surges and loss of power, shifting in and out and bucking, got to exit and it died within 5 minutes. Had it towed to garage thinking it was alternator (just got a new battery last week) and garage called me and said it started right up after the 2 hour tow and wait. Garage checked ALT and said it was good. Then drove several hundred miles (55 highway miles to work and back) for 2 days and fine, but then on highway began to notice slight loss of power cruising at 55-65 and could not accelerate. Slowed down to 50 and car starting bucking in gear (really almost slamming the trans back and forth) with gradual but quick loss of power(bucked between 40 to 30 and then down at 20 and then complete loss of power and died within 10 minutes.) Have just pulled the codes of 47 (Sub-Throttle position sensor signal) and know where that is located next to the TPS, but don't know its function and if it could disable the car like that (felt like no power and or gas). Also pulled a Code 35 (HAC sensor signal) and searched for Code 35 or explanation of what it is and can find almost nothing and don't know where it is, what it does and if it could disable the car like that? I also had an ECU rebuilt last year and it really improved everything. But when the car died, I decided today to switched it out with another one that I got at a salvage yard to see if it was the ecu and that is the one that is giving me the codes, but still cannot start the car, just turns over with no ignition or fire. Then I just plugged the rebuilt ecu from last year back in, to see if the same codes would come up and when I check those codes, it does not give me a code, just continual CEL blinking (so is this rebuilt ecu fried now?). IF ANYONE HAS ANY CLUE WHAT COULD BE WRONG, WITH A POSSIBLE FIX AND WHAT THE CODE 35 - HAC SENSOR SIGNAL? IS, I WOULD GREATLY APPRECIATE ANY ADVICE AND OR HELP. THANK YOU, THIS IS MY ONLY CAR AND STRANDED NOW. Thanks again and Appreciate your help, Tyndale Cobb

Yamae

The HAC sensor seldom fails. Even when it fails, the engine doesn't stop. When the ripple is too much, the ECU can't check the HAC sensor properly. Also many other analogue signals are nor properly processed. This is just my guess but most of your problems are related to the too much ripple to me. You can find the way how to check the ripple voltage at the FAQ page but some models need to check at the ECT sensor.

Are those capacitors properly replaced using correct capacitors? Didn't you have any trace damage?

You can't expect a lot on ECUs at salvage yards. But it is the often case that replacing QAS capacitors revives them. Why don't to try this using low ESR capacitors.