I have a 1990 300e California model. Here is the long sad story. Maybe one of you ace techs can point me in the right direction. I have searched and read everything I can find on this for the last 2 weeks.

I had a fuel leak from the EHA valve, my mechanic said that both the EHA and fuel distributer were leaking. I replaced both. Turns out the fuel distributor was OK, but I had already installed the rebuit one, so I left it in.

After I got done, I started getting an Check Engine light with code 17, High/Low O2 sensor. I replaced the O2 sensor with the 1990 Ford Mustang 302 unit. I checked the output voltage at the connector, it ran .05 to .85 volts. I was still getting the CEL. I was also intermittantly getting the ABS light, so as the result of some research, I replaced the OCP relay. This solved the ABS light problem but not the code 17 CEL error. I finally got the equipment together to moitor the EHA current, the Sears DVM to monitor duty cycle, and a third to monitor O2 voltage. I wired all 3 into the cockpit so I could monitor them during driving.

With the new O2 sensor, I am at about 82% duty cycle. EHA current runs from about 1- 6ma during driving. On sudden deceleration, it goes to about -45ma, then to 0. Duty cycle fluctuates between about 80 and 83. At idle, the EHA current slowly climbs from 2-4 to about 14ma, then the duty cycle drops from 80 to 10 in about 2 seconds, then drops to 0. As soon as I give it some gas, it pops back to 80 and the EHA current drops to 2-4ma.

I unplugged the O2 voltage wire and wired a AA cell into it. The duty cycle remained about 80-82, but the EHA current went to -10ma. Car barely ran. Took the battery off, plugged the O2 sensor back in, EHA went to 2-4ma again.

The only real symptom is the CEL, still code 17. The car seems to run fine, but I get the error again after a few minutes since clearing the code. Here are some observations.

It seems to be reading the O2 sensor, as applying 1.5 v to it sent the EHA current to the opposite extreme.

O2 sensor reads .45 until it hits op temperature. Then it fluctuated between .05 and .85 in response to the throttle.

Duty cycle on the controller doesn't drop below 80%, unless it drops to 10%, then 0.

I am afraid the car will not pass emissions unless I locate the problem. Any ideas?