Chevy Corsica V6: DTC-64 Manifold Sensor Circuit Signal Low

Asked by May 27, 2010 at 03:58 PM about the 1988 Chevrolet Corsica

Question type: Maintenance & Repair

Hi Everyone! I'm a newbie to this forum as well to Corsica's. I recently picked up a 1988 Corsica for a commuter that im trying to get to pass smog. Im having trouble with a DTC code 64. My programmer says its a MAP sensor circuit signal voltage low. From what Ive been reading low voltage= low pressure= high vacuum??? Any help to kill this fault code from popping up so i can pass smog would be great! The only symptoms the car is showing is a bit of a low idle and a very small hesitation on initial acceleration.

I found cracked vacuum hoses going to the MAP sensor as well as replaced the sensor with a brand new one. And unfortunately the code keeps popping up after I reset it. Any other suggestions???

Thanks for your help in advance!
Regards

3 Answers

10,235

The ECM uses the Manifold Absolute Pressure (MAP) sensor as an indication of engine load. High voltage would indicate low engine vacuum and higher engine load. Low voltage would indicate high engine vacuum and lower engine load. The ECM uses the information from this sensor to help calculate fuel delivery and spark timing. FYI: MAP sensors do not commonly fail. Erratic engine vacuum, as well as other engine performance problems can cause a code 64 Chances are extremely great that your engine is running lean. This can be caused by a bad O2 sensor, faulty fuel pressure regulator, or even something as simple as a clogged fuel filter. As far as symptoms of an engine running lean include hard starts and decreased power... I would recommend changing the typical maintenance items on a 20yr old car, and then work up from there.

Thanks for the help! I'm seeing a voltage low signal so it sounds like im probably running lean. However the car starts up immediately with the the turn of the key and seems to have reasonable power considering its a Corsica. (No signs on of a lean condition). I have recently done all the general tune up items like all fluids, filters, and plugs. However i have not taken a look at the 02 sensor. Ill try pulling it out and cleaning or swapping with a working one to see if i get any results. It has a new fuel pump, but i don't know about the regulator that seems to be a little bit more of a job to replace. Thanks for the help! Any other suggestions would be appreciated. Regards.....

10,235

Knowing all that you have replaced.. If the 02 sensor ($20 part) doesn't fix it and the car is running fine, I personally would just not worry about it. If the car is showing no signs of a lean condition, chances are, the car is just a victim of an old school garage mechanic. No lean condition.. High vacuum indicated... I would have to assume some vacuum lines have been capped off somewhere... If it is the fuel pressure regulator, it will get worse and eventually not start. GM uses vacuum controlled regulators and they bolt on the back side of the engine. They tend to fail in a closed position (creating a lean condition before they completely go out). Fairly easy to replace. Also not an expensive part if it does go out. But again, if it is not showing signs of a lean condition. I just wouldn't worry about it. FYI... The 2.8 v6 was a very peppy engine in the Corsica/Beretta line.. I had a '90 Beretta with the 2.8 and it would smoke the tires.

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