Well, I threw together a homemade pulse counter (thanks Arthur) and pulled some codes from my X11/4 diagnostic socket, and erased some others that had been fixed awhile back (O2 sensor ).

First thing I noticed is that my 16 pin X11/4 connector on firewall across from battery only has pins 1, 3, 6, 7, 14 occupied. According to my CD's and a diagram sent to me (thanks again Arthur) these pins diagnose the following:

1. ground
3. not used (why is a pin there?)
6. SRS control module
7. ACC push button control module
14. electronic accelerator control module/cruise control amplifier

No codes out of pin 14. Codes 3 and 29 from pin 3. These correlate to:

3 - Coolant temperature in KE control unit implausible
29- difference in coolant temperatures between KE control unit
and EZL ignition control unit.

WHICH TEMP SENSOR DO I NEED TO DIAGNOSE? ;D The test steps in CD manual mentions nothing about the 2 pin blue coolant sensor that cuts in high aux fans at 105 and cuts out AC at 115, rather the EZL coolant temp sensor (B11/2 -- big round 4 pin connector at back of head). Does the two pin blue coolant sensor have nothing to do at all with the CIS-E control unit??

Manual says to "measure temperature sensor connections diagonally and compare both readings -- they must be the same".

This is on the EZL sensor (4 pins) no doubt, so is this the 29 fault code I'm getting?

Thanks in advance for any insight any might have here ... my engine is still in FOM and the gas mileage is terrible.

'91 300 E