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No Upshift To Overdrive

  1. Warm engine to normal operating temperature. With ignition off, disconnect solenoid harness connector from transmission. Electrical connectors are located near park/neutral position switch on transmission.
  2. Road test vehicle and note if transmission upshifts to overdrive. Reconnect harness connector. Clear codes from ECU memory, as disconnecting electrical connectors may set codes. Refer to CLEARING FAULT CODES . If no overdrive upshift exists, disassemble and inspect transmission. If overdrive upshift exists, go to next step.
  3. Connect voltmeter between terminals TT and E1 of DLC connector. See Figure and Figure . Road test vehicle and ensure voltage at terminal TT increases from zero to 7 volts. See GEAR SIGNAL  under ELECTRICAL TESTING.
  4. If no voltage exists, check for 10-14 volts between terminals L and E1 on ECT ECU with the connector connected, the shift lever in the "D" position and with ignition on. See Figure. If 10-14 volts exist, check for defective park/neutral position switch. Refer to PARK/NEUTRAL POSITION (PNP) SWITCH  under COMPONENT TESTING.
  5. If switch is okay, inspect and repair circuit(s) between switch and ECT ECU. See appropriate wiring diagram in WIRING DIAGRAMS . If 10-14 volts does not exist, replace ECT ECU.
  6. If voltage increases from zero to 2 volts, check for 10-14 volts between terminals 2 and E1 on ECT ECU with connector connected, shift lever in "D" position and ignition on.
  7. If 10-14 volts exist, check for defective park/neutral position switch. If switch is okay, inspect and repair circuit(s) between switch and ECT ECU. See appropriate wiring diagram in WIRING DIAGRAMS. If 10-14 volts does not exist, replace ECT ECU.
  8. If voltage increases from zero to 7 volts between terminals L and E1, solenoids may be faulty. See SOLENOIDS  under COMPONENT TESTING. If solenoids are okay, disassemble and inspect transmission. If voltage increases from zero to 4 volts between terminals L and E1, connect voltmeter between terminals OD2 and E1 on ECT ECU with connector connected. See Figure.
  9. Turn ignition on. Check voltage with OD switch on the shift lever released (OFF position) and depressed (ON position). No voltage should exist with switch released and 10-14 volts should exist with switch depressed.
  10. If voltage is correct, go to next step. If voltage is not as specified, check for defective OD switch or wiring circuit.
  11. Check voltage between terminals OD1 and E1 on ECT ECU with connector connected and ignition on. Voltage should be approximately 5 volts. If voltage is correct, replace ECT ECU. If voltage is not correct, go to next step.
  12. Disconnect electrical connector from cruise control ECU. See Figure-Figure . Check voltage between terminals OD1 and E1 on ECT ECU with connector connected and with ignition on. If voltage is approximately 5 volts, replace cruise control ECU. If voltage is not within specification 5 volts, inspect and repair circuit(s) between cruise control ECU and ECT ECU. See appropriate wiring diagram in WIRING DIAGRAMS . If wiring is okay, replace ECT ECU.
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