Recently I have been getting pretty poor gas mileage (15-16 mpg on average) when I used to get around 20 mpg. The SES light has been comming on pretty frequently, but only comes on for a short period of time then turns off. The car was scanned with C.A.T.S and it came up with code 24: output speed low, and code 34: map low. I have no idea what these mean. Do I have a bad map sensor? And even more confusing, what does "output speed low" mean? Any help would be appreciated. Thanks.

 

DTC 24 is for the vehicle speed sensor. Could be the VSS sensor is faulty or the wiring is damaged.

DTC 34 (MAP signal voltage low/vacuum high) sets when the MAP is below 14kPA at idle, or below that level when the engine is above 1,200rpm and the throttle position is greater than 21%. That could be the result of a crumbling wire harness connector on the MAP sensor - not an unusual problem. They dry out and fall apart.

 

Where is the Vehicle speed sensor located?

The wires leading to the connector on the map sensor look to be in good shape, there doesnt seem to be much corrosion or deterioration that I can tell. I'm guessing that this wouldn't necisarily rule out a bad wire right? Or were you saying that the connector itself is the more likely part to break?

And another thing (although i don't know whether or not its of any importance) is that a few times I have noticed that when the SES light comes on at low speeds (under 5mph) the fans kick on, and when the fans stop the light also turns off. The problem is that I dont know which code it's throwing at that time.

Thanks

 

The vehicle speed sensor is located on the tailshaft of the transmission:

http://cjcfo.fbody.com/members/injun...E/T56Conns.jpg

The MAP sensor harness connectors dry out and crumble, allowing the terminals to shift. Just a possibility... I know mine just fell apart in my hand when I tried to unplug it. I deteermined there was a problem by looking at a data log and finding that at WOT when the MAP sensor should have been reporting close to 100kPA constantly, it was intermittently dropping to "0".

You can check the wiring. The black wire is a ground, the gray wire supplies +5V reference, and the light green wire puts out a voltage signal that varies with manifold absolute pressure. To get 14kPa or less and trip the code, you would be seeing about 0.45V between the light green and black wires at idle. You should be seeing about 35kPa (1.4V) at idle. This is a good application for a scanner that will access the sensor readings. Verify that you have 5V between the black wire and the gray wire with the key on engine off.

Several codes will turn the fans on.