KOEO IVSC Problem - Anyone?

[HighRev85]

Hey all,

I've searched far and wide to find out why this test won't work to no avail.

I've included the copy I've been following. I'm running the test on a 95 MTX. The vacuum lines are attached, vacuum dump intact and functional, and the clockspring is working correctly (horn works). Any thoughts as to why the process isn't working? Has anyone done this who has some thoughtful insight?

Thanks for all the help in advance!


IVSC SELF-TEST

Key On, Engine Off and Engine Running tests can check the IVSC system by testing its functional capability and verifying that various sensors and actuators are connected and operating properly. The KOEO and KOER IVSC tests are functional tests which only detect concerns present at the time of the Self Test.

To activate KOEO IVSC test, do the following:

1. Place transmission shift lever in PARK.

2. Hook up your multimeter in accordance with the regular EEC-IV code-pulling procedures (see http://www.dalidesign.com/hbook/eectest.htm)

3. Turn ignition switch to RUN position.

4. Within 10 seconds, press speed control ON switch.

5. Press speed control OFF, COAST, ACCEL, RESUME buttons; tap brake pedal once.

NOTE: Do not depress throttle during KOEO self-test.

6. Observe and record all Diagnostic Trouble Codes indicated.

DTC 452 = VEHICLE SPEED SENSOR (VSS) PROBLEM.
(Note: This code is actually stored by the regular EEC-IV monitor(s), not the IVSC system monitor. Hence, it’s probably a good idea to run the codes in the regular manner before doing the IVSC system test in order to see if this VSS code comes up).

DTC 453/454 = DOES NOT HOLD SPEED DURING DYNAMIC TEST
Possible Causes:
- Speed control servo.
- Vacuum hose connections.
- Speed control vacuum reservoir
- Speed control vacuum valve.

DTC 455 = SPEED DOES NOT INCREASE DURING DYNAMIC TEST
Possible Causes:
- Actuator cable.
- Vacuum hose connections.
- Speed control dump valve adjustment.
- Powertrain control module.
- Speed control vacuum reservoir.
- Speed control vacuum valve.

DTC 456 = SPEED DOES NOT DECREASE DURING DYNAMIC TEST
Possible Causes:
- Actuator cable.
- Throttle shaft and linkage.
- Throttle position sensor (TPS).
- Powertrain control module.

DTC 457/458/459 = SPEED CONTROL SWITCHES
Possible Causes:
- Speed control actuator switch assembly.
- Air bag sliding contact.
- Wiring harness.
- Powertrain control module.

DTC 567/568 = SERVO SOLENOIDS
Possible Causes:
- Servo vent solenoid.
- Servo vacuum solenoid.
- Circuits SOL+, SCVNT, and SCVAC.
- Powertrain control module.

 

[projectSHO89]

The horn's operation is not a definitive proof og the clockspring's integrity. There are more conductors used only by the VSC system.

Step #1 probably also gave you a problem.

Steve

 

[firstgen89sho]

speed control runs off of a different set of wires, compared to the horn and airbag.

 

[projectSHO89]

speed control runs off of a different set of wires, compared to the horn and airbag.

Actually, it uses both wires for the horn plus a discrete wire all to itself. The airbag circuit is all to itself.

Steve

 

[HighRev85]

Went into the EEC to test the continuity of the wires and ensure that the clockspring is working correctly (someone had posted a cruise control diagnostic for an 89 MTX - I followed that). The switches are working correctly, but the IVSC is STILL not working .

So yes, the clockspring is working. I also double-checked that the cable is still connected to the throttle linkage and that all the vacuum lines are tight.

Anyone have any thoughts? Or is this a test that can only be run on an ATX? I'd rather not go through and start replacing parts...

I swear, the worst part about the SHO is that it makes you a perfectionist