Important! Base timing on 81

[GerryLP]

Al,

The terminals are the ones connecting the computer. And I am sure that you are aware that inside the battery compartment, is the ECM. Which means you have to remove the battery if like me, you have big hands because it is a PITA to attempt troubleshooting it with it on the way, and besides, the harness is only long enough to disconnect it from it.

The smaller connector has the terminals identified with letters. The bigger one has numbers on the terminals. You'll need the wiring diagram in your new shop manual.

Without looking at the troubleshooting chart, if it tells you to look for shorts, then it is having you check the terminal to see if you are getting the required signal. Once you get the correct reading, it has been my experience that the open or short would most likely be found relatively far from the ECM, so follow the wire associated with the terminal/signal and see where it takes you. Unless you have messed recently with the harnesses within the passenger compartment, the ods are that the problem is near the sensor or components it connects to.


GerryLP

 

[TimAT]

Hi Guys my shop manual said 2 far right terminals to diagnose. When I did that i got my check engine light flashes constantly. Now it says to check terminal 21 on ECM for voltage, then depending over or under 4 volts determines checking if ECM 5 or ECM 19 is grounded. Problem is i dont know where to find these terminals are or how to check if they are grounded. Can someone tell me where to find them

Thanks Al

The check engine light WILL flash constantly when the terminals are jumpered. Correct operation. GO back up this thread- there was a post on the sequence and how to count the flashes to figure out what codes are set, along with a list of codes.
Remember- in 1981, the ECM/CCC system was really in it's infancy. All the scan tools did was make it faster for the dealers to troubleshoot. The manuals have everything you need to corrrectly diagnose and fix anything in the system. How to adjust the TPS, mixture control- it's all in there. A scan tool just gives you a quick readout without a bunch of unplugging and building jumper wires.