98 RENR5042-02 Troubleshooting Section Expected Result: Repair: Verify the continuity of the wire for the overspeed verify switch to the negative battery. Close the overspeed verify switch and measure the continuity from P1-54 to the negative battery. If the wire does not have continuity to the negative battery, repair the wire and/or replace the overspeed verify switch. The test lamp illuminated when the engine speed increased past 75 percent of the programmed overspeed setpoint. Results: OK The test lamp illuminated. Verify the continuity of the wire from the coil of the air shutoff relay to the ECM connector P1-67 before proceeding. Proceed to Test Step 6.
If the wire for the overspeed verify switch has continuity to the negative battery, there is a problem in the wiring between P1-11 and the air shutoff relay. Repair the circuit connectors or wiring and/or replace the circuit connectors or wiring. Verify that the problem is resolved. Not OK The test lamp did not illuminate. The voltage from the ECM was not present at the coil of the air shutoff relay. Proceed to Test Step 5. STOP. Test Step 5. Short the Overspeed Verify Switch at the ECM Not OK – The test lamp did not illuminate. Repair: Perform the following procedure: A. Turn the keyswitch to the OFF position. B. Disconnect ECM connector P1. 1.
Remove all jumpers and reconnect all terminals. C. Remove terminal P1-54 (overspeed verify switch). 2. Temporarily install a new ECM. Refer to Troubleshooting, “Replacing the ECM”. D. Insert one end of a wire jumper into the socket for P1-54 (overspeed verify swtich). Connect the other end of the wire jumper to engine ground. 3. Check the system for active diagnostic codes. 4. Perform this Test Step again. E. Remove terminal P1-11 (air shutoff solenoid). 5. If the problem is resolved with the test ECM, reconnect the suspect ECM. Verify that the problem returns. If the problem returns with the suspect ECM, replace the ECM. F.
Insert one end of the wire jumper into the socket for P1-11 (air shutoff solenoid). G. Connect one lead of the test lamp to the other end of the jumper wire in P1-11 (air shutoff solenoid). 6. Verify that the problem is resolved. STOP. H. Connect the other lead of the test lamp to negative battery. Test Step 6. Test the Diode for Current Flow in One Direction I. Start the engine. J. Activate the overspeed verify switch. K. Monitor the test lamp while you increase the engine speed past 75 percent of the programmed overspeed setpoint. Expected Result: g00761537 Illustration 23 The test lamp illuminated when the engine speed increased past 75 percent of the programmed overspeed setpoint.
Diode A. Disconnect the wires from the air shutoff relay. Results: B. Remove the diode from the air shutoff relay. OK – The test lamp illuminated. C. Put the digital voltmeter (DVM) in “Diode Check”.