Computer Code 623
 

I'm getting a code 623 on a 95 Mazda 626 4 cylinder. Does anyone know what this code means?

RE: Computer Code 623
 

Is this a manual or auto transmission? Although there is no code 623.

RE: Computer Code 623
 

It'a an Automatic.
I found one web site that listed the code as "Transmission Control Indicator Lamp Circuit Failure".
Any idea what this means? The transmission works fine, except I do have a problem when idling at stop lights after the car has warmed up and after you have ben stopped for a few minutes.

RE: Computer Code 623
 

Was the CEL or HOLD light on that would have prompted you to check for any codes? Also does the O/D switch and light on the dash function normally? This code is often set if you fail to cycle the O/D off button when startiing the KOEO (Key On Engine Off) self test. You know the point where the tester says actuate BOO, PSP, and mode switch. O/D off button is the mode switch that needs to be cycled. If you fail to cycle the switch during KOER (Key On Engine Running) self test it will store a code 653 instead.

RE: Computer Code 623
 

I am having an idle problem after the car warms up. I've cleaned the IAC, and just tried to check the codes to see if there were any. There weren't any lights on to begin with. What's the difference between the CEL and HOLD light?
I didn't activate anything when I checked for the codes. I got the 623 when I just jumpered and turned the key to the ON position. When I had the jumper on and started the car, I got the following codes: 172 536 521 and 653. But, again I didn't activate the BOO,PSP or Mode switch. I wasn't using a tester, I just jumpered the test contact and counted the CEL flashes. I guess that accounts for the 536,521, 653 and 623 code. So should I just worry about the 172 (oxygen sensor) code?
WIthout having a tester hooked up, is there a way to tell when you should activate the BOO, PSP, etc.?

RE: Computer Code 623
 

No there is not a way to tell when to do it other then when using a tester. You might try activating all three just after you jumper to ground. Otherwise just ignore them now that you know what they mean. The 536 is brake switch failiing to change and 521 is no change in PSP signal. 172 is the important one. It is indicating that the oxygen sensor is not switching and is lean. This does not necessarily mean a bad oxygen sensor but only that it is indicating a lean condition. A vacuum leak can create the same type of problem. Have you checked carefully for vacuum leaks? Intake manifold gaskets are notorious leakers on that engine but also look for any vacuum lines off or tees broken. If you have a decent voltmeter then tap into the oxygen sensor signal wire (that would be the yellow one), and see what the voltage is doing. It should be cycling between approx 0-1 Volt roughly every second at idle and even faster with the rpm raised. Below 450 millivolts is a lean condition and above 450 millivolts is a rich condition.

RE: Computer Code 623
 

Thanks a lot for the information. I'll try to check out hte O2 Sensor as soon as I get a chance.

RE: Computer Code 623
 

Ford sure made diagnosis more difficult than it had to be. Why in the world did Mazda get mixed up with them?!?!

RE: Computer Code 623
 

Well, it looks like it's the intake manifold. I can spray some starting fluid at one point and get the idle to smooth out.

RE: Computer Code 623
 

Well, I had the Intake Gasket replaced (it had a break in it), the valve cover gasket replaced and new plugs and wires due to shorting at the plugs due to oil seepage.
AFter all of the, the car idles steadier and does not stall (yet), but still shakes pretty bad when in gear, stopped at a stop light.
Any ideas what else this could be?