A good multimeter tells all on the 86 300e. The fault memory (only active no stored codes on 86-87) is read on pin #3 of the diagnostic socket. Set your meter on duty-cycle and read the value. If you have closed-loop oxygen sensor control you will have a roving duty-cycle; lean and rich about 50% if all is adjusted properly.
If you get a constant duty-cycle it will indicate a given problem 10%, 20%, 30%, etc.
Email if you need a code chart.
To guarantee proper meter set-up. Turn key on, engine off, and you should read 70% on a Federal version car and 85% on a CA version.
If you really want to watch the whole system use your amp-meter section and hook in series to read the EHA current. The EHA (electro-hydraulic actuator) is the mechanical result of all the electronic sensing. It is a controlled leak to the upper chamber pressure of the fuel distributtor.
The amp readings will be in the -60 to +100ma range. There will be a 40+ma current for starting enrichment, 20-30 for cold enrichment, maybe 10ma for acceleration enrichment AND about 10+ and 10- milliamps of O2 sensor correction.
Once warm the value of the current flow would be 0.0ma if the O2 sensor was disconnected. When hooked up the closed loop control should have the milliamp value hovering plus or minus one or two milliamps. If it ranges from -6 to -3 and back the system would be in closed loop but too rich so the mixture is being leaned out (-ma = too rich +ma = too lean.
The relative value of your oxygen sensor can be judged by the rate of the lean/rich correction during these cycles. The sensor should be hot and the engine speed at 2000rpm long enough to stabilize.
[This message has been edited by Webmaster (edited 03-14-2000).]