Switch Test Procedure

Code .7.0 must be displayed on the ECC control head before the switch tests can begin. To start the switch tests sequence depress and release the brake pedal; the switch tests begin as the display switches from Code .7.0 to Code .7.1, see Figure 8D1-4. (If the display doesn’t advance to Code .7.1, refer to the diagnosis chart, Code .7.1, because the ECM is not processing the brake signal.)

As each code is displayed, the associated switch (see Figure 8D1-5), must be cycled within 10 seconds or the code will be recorded in the ECM’s memory as a failure. After the ECM recognizes a test as passing or after the 10 second time-out elapses without the proper cycling being recognized, the display automatically advances to the next switch test code. The switch tests sequence is performed as follows:

1.     With Code .7.1 displayed, depress and release the brake pedal again to test the Cruise Control brake circuit.

2.      With Code .7.2 displayed, depress the throttle from the idle position to an open throttle position and then slowly release the throttle.
While this action is being performed, the ECM checks the throttle switch for proper operation.

3.        With Code .7.3 displayed, shift the transmission lever into drive and then neutral. This action checks the operation of the drive switch.

4.        With Code .7.4 displayed, shift the transmission lever to reverse and then into park. This action
checks the operation of the reverse switch.

On cars without Cruise Control, codes .7.5, .7.6 and .7.7 will be displayed but cannot be performed during the switch tests. When these codes are displayed during the switch tests, allow the code to reach it’s 10 second time out. After this time out has elapsed, the display will advance to the next code. Allow codes .7.5, .7.6 and .7.7 to time out (30 seconds). Since these codes will be recorded as failures in the switch tests sequence, a display of .0.0 will never be observed at the completion of the tests (see Step # 12). To confirm proper operation of the remaining switches, codes .7.8, .7.9 and .8.0 must be observed as having advanced within their 10 second time out. If the code cannot be advanced within its time out, it should be considered a failed test.

5.        With Code .7.5 displayed, switch the Cruise Control instrument panel switch from off to on and back to off to check the operation of this switch.

6.      With Code .7.6 displayed and with the cruise instrument panel switch in the on position, depress and release the set/coast button to check the operation of this switch.

7.      With Code .7.7 displayed and with the cruise instrument panel switch in the on position, depress and release the resume/acceleration switch to check the operation of this switch.

8.      With Code .7.8 displayed, depress and release the “instant/average” button on the Fuel Data panel to test the operation of this switch.

9.        With Code .7.9 displayed, depress and release the “reset” button on the Fuel Data panel to test the operation of this switch.

10.      With Code .8.0 displayed, depress and release the “outside temperature” button TWICE.
When diagnostics are first entered, compressor clutch
engagement is commanded as indicated by the “outside temperature” status light being on. When the “outside temperature” button is pushed the status light will go out and the clutch should disengage. When the button is pushed the second time the status light will come back on and the clutch should reengage. This action checks the ECM’s ability to recognize and process the air conditioning clutch signal. However, the compressor cycling switch in series with the compressor drive circuit must be closed in order to energize the A/C compressor clutch. Sometimes, the engine may need to be running and the ECC may need to be operating in auto and 60’F to close the contacts of the compressor cycling switch.

11.      When the switch tests are completed, the ECM will now go back and display the switch codes which did not test properly. Each code which did not pass will be displayed beginning with the lowest number. The codes will not disappear until the affected switch circuit has been repaired and retested. Refer to the appropriate diagnosis chart for each trouble code.

12.      After the switch tests are completed and all circuits pass, the ECC panel displays “.0.0” and then returns to Code .7.0. “.0.0” indicates that all of the switch circuits are operating properly.