Procedures
1. Remove the cover below the glove box and the MPI relay to gain access to the ECM.
2. Check the knock sensor wiring harness by disconnecting the Engine Control Module (ECM) harness connectors and the knock sensor 2-pin connector. Perform a resistance check of the wires.
2a. Using a volt/ohm meter, insert one test lead onto Pin # 1 of the harness-side of the knock sensor harness. Ground the other test lead. No continuity (infinite resistance) should be present. If continuity is present a short exists, so repair the Pin # 1 wire and re-test.
2b. Insert one test lead onto knock sensor wiring harness Pin # 2. Ground the other test lead. Continuity (no resistance) should be present. If there is no continuity, repair the # 2 wire and re-test.
2c. Insert one test lead into Pin # 58 of the ECM harness. Ground the other test lead. No continuity (infinite resistance) should be present. If continuity is present then a short exists, so repair the Pin # 58 wire and re-test.
2d. Reconnect all connectors separated in step 2. Reinstall the MPI relay and proceed to step 3.
3. Using the chart, check the vendor number of the ECM. If the vehicle is equipped with the new style ECM, go to step 18. If the ECM is the old style, go to step 4 and proceed with installing the Knock Sensor Modulator Kit.
4. Erase DTC 31 using the Scan Tool.
5. Record the radio presets and disconnect the negative battery terminal.
6. For easier access to the ECM and harness connectors, remove the MPI relay, then disconnect the wiring harness connectors from the ECM.
7. Obtain a Knock Sensor Modulator Kit, part number MD315493.
The kit contains 3 parts:
^ Part # 1: Modulator Harness
^ Part # 2: Adapter Plug
^ Part # 3: Modulator
8. Attach the individually wrapped long harness leads with white connectors to either side of the adapter plug as shown.
9. Attach the clear 9-pin connector of the modulator harness to the modulator assembly.
10. Attach the three remaining white connectors (short, NOT individually wrapped harness leads of the modulator harness) to the ECM.
11. Attach the ECM wiring harness connectors to the open end of the adapter plug.
12. Remove the double-stick foam tape cover strip on the adapter and secure the adapter to the ECM. Remove the double-stick foam tape cover strip on the modulator then secure the modulator to the lower glove box cover.
13. Reinstall the MPI relay.
14. Attach the negative battery terminal, set the clock: and reset radio presets.
NOTE:
If power to the radio was interrupted for more than one hour: the radio security code (if so equipped) must be re-entered.
15. To confirm proper installation, perform the following steps:
15a. Start the engine and let idle for 30 seconds.
15b. Locate the MPI relay.
15c. With one hand on the MPI relay, turn the ignition key to the OFF:: position. Notice the relay will click immediately after the ignition is turned off and will click a second time usually within 5 seconds.
15d. If the relay does not click a second time: the harness may be installed backwards. If the desired results are not observed, or you are not certain of the results, repeat steps 15a through 15c to confirm operation. If the MPI relay does not click twice after repeating steps 15a - 15c, start with step 6 and repeat the modulator kit installation procedures.
NOTE:
If the MPI relay does not click twice after the ignition is turned off, the MPI relay will stay energized, draining the battery.
16. Install the cover below the glove box.
17. Perform the following test drive:
17a. Erase DTC31 using the Scan Tool.
17b. Verify non-illumination of the "Check Engine" light.
17c. Drive the vehicle until normal operating temperature is reached.
17d. Decelerate (foot off accelerator pedal) down a grade steep enough to maintain 2,500 mm for 4 seconds.
17e. Return the vehicle to the shop. Using the Scan Tool, check for DTC 31.
If DTC 31 is not present, return the vehicle to the customer.
If DTC 31 is still present, go to step 18.
18. Replace the knock sensor as outlined on page 13A-381 of the 1992-96 Diamante Service Manual, Volume 1. After replacing the knock sensor, confirm that the repair was effective by repeating test drive procedures in step 17.