ECM Questions

[Shannen Durphey]

Jason, here's what I can tell.  This is very similar to
other Chrysler systems.  

Jason Weir wrote:
> 
> I have got the pinout of the computer out of a 91-95 Jeep Wrangler and I
> thought that I might get some of the more educated than I to take a
> looksie and tell me what they interpret out of it...
> 
> 1. Map Signal
> 2. Coolant Temp Signal
> 3. Battery 12V Fused
> 4. Sensor Ground
> 5. Ground
> 6. 5 Volt Supply   -----  5 volts out to sensor?  I assume
5V is usually TPS and MAP.  Sensor ground is a return from
those same sensors.

> 7. 8 Volt Supply   -----  any ideas for what? Sensors??
> 8. not used
> 9. Ignition Switched 12V Fused
> 10. not used
> 11. Ground
> 12. Ground
> 13. Injector #4 Driver
> 14. Injector #3 Driver
> 15. Injector #2 Driver
> 16. Injector #1 Driver
> 17. not used
> 18.  not used
> 19. Ignition Coil #1 Driver   ----- can anybody explain how this works

Does this have a distributor?  This probably controls the
ground path for the coil.

> 20. Generator Field Driver  ----- I assume to excite the alternator?

Generator field driver grounds the field, ECU acts as
voltage regulator.  

> 21. IAT Sensor Signal
> 22. TPS Signal
> 23. not used
> 24. Crankshaft Position Sensor Signal
> 25. SCI Transmit  --- another, what the heck is this

SCI is probably communication bus for other connected
systems.  ABS, instrument cluster, airbag are all guesses
there.  

> 26. not used
> 27. A/C Switch Sense   ---- Ok
> 28. A/C Switch Sense   ---- does it need 2?

 A/C Switch sense probably low/high pressure switches. 

> 29.  Stop Lamp Switch Sense
> 30. Park/Neutral Position Sense
> 31. not used
> 32. SES Light
> 33. not used
> 34. A/C Relay Control  ----- apparently the computer reads the switch
> and controls the relay???
  ECM controls compressor, watches on/off switch, high/low
pressure switches.
> 35. not used
> 36. not used
> 37.  not used
> 38. Injector #5 Driver
> 39. IAC Motor #1 Driver   ---  why 4 IAC drivers????
IAC uses stepper motor.  Requires 4 connections to ECU. 
Stepper motors allow more precise control of motor position
than regular DC motors.
> 40. IAC Motor #3 Driver
> 41. O2 Sensor Signal
> 42. not used
> 43. Tach Signal
> 44. Cam Position Sensor Signal
> 45. SCI Receive   ----- Anybody have any idea what SCI is
> 46. not used
> 47.  VSS
> 48. not used
> 49.  not used
> 50. not used
> 51. Automatic Shut Down Relay Control   ------ again no idea what this is
ASD relay turns off power for coil, fuel pump, and possibly
A/C and fan relays.  This is GND side.
> 
> 52. not used
> 53. not used
> 54. Upshift lamp driver
> 55. not used
> 56. not used
> 57. Automatic Shut Down Relay Output   ---- another one here
This be power for the coil for the ASD relay. 

> 58. Injector #6 Driver
> 59. IAC Motor #4 Driver
> 60. IAC Motor #2 Driver
> 
> The idea here is to replace or piggyback the stock, never has been
> reverse engineered enough to do anything with computer with a GM unit
> which has a wealth of info on it available.  Making it feasible to do
> engine mods and be able to reprogram the computer.  As of now I know of
> only one or two companies that make a so called performance "chip" for
> this vehicle.  And even this isn't a true "chip" in the sense it is a
> module that plugs inline between the harness and computer...Even with
> this chip any upgrades other than exhaust and before the throttle body
> intake stuff oh yeas and the 20 degrees cooler thermostat will still set
> a code...Any ideas?  later,  Jason

Give me some specifics, engine size, options, exact year,
and I can get you some schematics and give you better info
about the pins' function, including a possible cross to GM
terminology where needed.

Shannen