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DTC 28









DTC 28: Park/Neutral Position Switch System (Short Circuit)

CIRCUIT OPERATION
^ Battery positive voltage is applied to the Park/Neutral position switch (terminal 8) when the ignition switch is turned "ON."
^ Battery positive voltage is applied to the PCM (terminal 101) when the selector lever is in the "P" range. The PCM judges that the selector lever is in the "P" range when the battery positive voltage is applied.
^ Battery positive voltage is applied to the PCM terminal 108 (121, 102, 109, 122 or 110) when the selector lever is in the "R" range ("N." "D," "3," "2" or "L" range). The PCM judges that the selector lever is in the "R" range ("N." "D," "3," "2" or "L" range) when the battery positive voltage is applied

DTC SET CONDITIONS
If the PCM detects more than one park/neutral position switch input signal for thirty seconds, it is determined that there is a short circuit in the Park/Neutral position switch and DTC 28 is set.

TROUBLESHOOTING HINTS
(The most likely causes for this code to be set are:)
^ Malfunction of the Park/Neutral position switch
^ Malfunction of the ignition switch
^ Damaged harness or connector
^ Malfunction of the PCM

DIAGNOSIS

Required Special Tool:
^ MB991502: Scan Tool (MUT-II)

STEP 1. Check the Park/Neutral position switch. Measure the resistance between the terminals for each selector position as indicated in the table above.











Q: Is the measured resistance less than 2 ohms for each selector position?
YES: Go to Step 2.
NO: Replace the Park/Neutral position switch

STEP 2. Check Park/Neutral position switch connector B-16 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q: Are the connector and terminals in good condition?
YES: Go to Step 3.
NO: Repair or replace the damaged components

STEP 3. Check PCM connector C-114 for loose, corroded or damaged terminals, or terminals pushed back in the connector.





Q: Are the connector and terminals in good condition?
YES: Go to Step 4.
NO: Repair or replace the damaged components.

STEP 4. Measure the switch output voltage at PCM connector C-114 by backprobing. ("P" position)





1. Do not disconnect connector C-114.
2. Turn the ignition switch to the "ON" position.





3. Measure the voltage between terminal 101 and ground by backprobing.
^ When selector lever position is "P." voltage should measure battery positive voltage.
^ When selector lever position is "R." voltage should measure 0.5 volt or less.
^ When selector lever position is "N." voltage should measure 0.5 volt or less.
^ When selector lever position is "D," voltage should measure 0.5 volt or less.
^ When selector lever position is "3," voltage should measure 0.5 volt or less.
^ When selector lever position is "2," voltage should measure 0.5 volt or less.
^ When selector lever position is "L," voltage should measure 0.5 volt or less.
Q: Is the measured voltage within the specified range?
YES: Go to Step 6.
NO: Turn the ignition switch to the "LOCK" (OFF) position. Go to Step 5.

STEP 5. Check harness for open circuit or short circuit to ground between Park/Neutral position switch connector B16 terminal 3 and PCM connector C-114 terminal 101.








Q: Is the harness wire in good condition?
YES: Go to Step 18.
NO: Repair or replace the harness wire.

STEP 6. Measure the switch output voltage at PCM connector C-114 by backprobing. ("R" position)





Measure the voltage between terminal 108 and ground by backprobing.
^ When selector lever position is "P." voltage should measure 0.5 volt or less.
^ When selector lever position is "R." When selector lever position is "P." voltage should measure battery positive voltage.
^ When selector lever position is "N." voltage should measure 0.5 volt or less.
^ When selector lever position is "D," voltage should measure 0.5 volt or less.
^ When selector lever position is "3," voltage should measure 0.5 volt or less.
^ When selector lever position is "2," voltage should measure 0.5 volt or less.
^ When selector lever position is "L," voltage should measure 0.5 volt or less.
Q: Is the measured voltage within the specified range?
YES: Go to Step 8.
NO: Turn the ignition switch to the "LOCK" (OFF) position. Go to Step 7.

STEP 7. Check harness for open circuit or short circuit to ground between Park/Neutral position switch connector B16 terminal 7 and PCM connector C-114 terminal 108.








Q: Is the harness wire in good condition?
YES: Go to Step 18.
NO: Repair or replace the harness wire.

STEP 8. Measure the switch output voltage at PCM connector C-114 by backprobing. ("N" position)





Measure the voltage between terminal 121 and ground by backprobing.
^ When selector lever position is "P." voltage should measure 0.5 volt or less.
^ When selector lever position is "R." voltage should measure 0.5 volt or less.
^ When selector lever position is "N," voltage should measure battery positive voltage.
^ When selector lever position is "D," voltage should measure 0.5 volt or less.
^ When selector lever position is "3," voltage should measure 0.5 volt or less.
^ When selector lever position is "2," voltage should measure 0.5 volt or less.
^ When selector lever position is "L," voltage should measure 0.5 volt or less.
Q: Is the measured voltage within the specified range?
YES: Go to Step 10.
NO: Turn the ignition switch to the "LOCK" (OFF) position. Go to Step 9.

STEP 9. Check harness for open circuit or short circuit to ground between Park/Neutral position switch connector B16 terminal 4 and PCM connector C-114 terminal 121.








Q: Is the harness wire in good condition?
YES: Go to Step 18.
NO: Repair or replace the harness wire.

STEP 10. Measure the switch output voltage at PCM connector C-114 by backprobing. ("D" position)





Measure the voltage between terminal 102 and ground by backprobing.
^ When selector lever position is "P," voltage should measure 0.5 volt or less.
^ When selector lever position is "R," voltage should measure 0.5 volt or less.
^ When selector lever position is "N," voltage should measure 0.5 volt or less.
^ When selector lever position is "D," voltage should measure battery positive voltage.
^ When selector lever position is "3," voltage should measure 0.5 volt or less.
^ When selector lever position is "2," voltage should measure 0.5 volt or less.
^ When selector lever position is "L," voltage should measure 0.5 volt or less.
Q: Is the measured voltage within the specified range?
YES: Go to Step 12.
NO: Turn the ignition switch to the "LOCK" (OFF) position. Go to Step 11.

STEP 11. Check harness for open circuit or short circuit to ground between Park/Neutral position switch connector B-16 terminal 1 and PCM connector C-114 terminal 102.








Q: Is the harness wire in good condition?
YES: Go to Step 18.
NO: Repair or replace the harness wire.

STEP 12. Measure the switch output voltage at PCM connector C-114 by backprobing. ("3" position)





Measure the voltage between terminal 109 and ground by backprobing.
^ When selector lever position is "P," voltage should measure 0.5 volt or less.
^ When selector lever position is "R," voltage should measure 0.5 volt or less.
^ When selector lever position is "N," voltage should measure 0.5 volt or less.
^ When selector lever position is "D," voltage should measure 0.5 volt or less.
^ When selector lever position is "3," voltage should measure battery positive voltage.
^ When selector lever position is "2," voltage should measure 0.5 volt or less.
^ When selector lever position is "L," voltage should measure 0.5 volt or less.
Q: Is the measured voltage within the specified range?
YES: Go to Step 14.
NO: Turn the ignition switch to the "LOCK" (OFF) position. Go to Step 13.

STEP 13. Check harness for open circuit or short circuit to ground between Park/Neutral position switch connector B-16 terminal 5 and PCM connector C-114 terminal 109.








Q: Is the harness wire in good condition?
YES: Go to Step 18.
NO: Repair or replace the harness wire.

STEP 14. Measure the switch output voltage at PCM connector C-114 by backprobing. ("2" position)





Measure the voltage between terminal 122 and ground by backprobing.
^ When selector lever position is "P." voltage should measure 0.5 volt or less.
^ When selector lever position is "R." voltage should measure 0.5 volt or less.
^ When selector lever position is "N." voltage should measure 0.5 volt or less.
^ When selector lever position is "D," voltage should measure 0.5 volt or less.
^ When selector lever position is "3," voltage should measure 0.5 volt or less.
^ When selector lever position is "2," voltage should measure battery positive voltage.
^ When selector lever position is "L," voltage should measure 0.5 volt or less.
Q: Is the measured voltage within the specified range?
YES: Go to Step 16.
NO: Turn the ignition switch to the "LOCK" (OFF) position. Go to Step 15.

STEP 15. Check harness for open circuit or short circuit to ground between Park/Neutral position switch connector B16 terminal 2 and PCM connector C-114 terminal 122.








Q: Is the harness wire in good condition?
YES: Go to Step 18.
NO: Repair or replace the harness wire.

STEP 16. Measure the switch output voltage at PCM connector C-114 by backprobing. ("L" position)





Measure the voltage between terminal 110 and ground by backprobing.
^ When selector lever position is "P," voltage should measure 0.5 volt or less.
^ When selector lever position is "R," voltage should measure 0.5 volt or less.
^ When selector lever position is "N," voltage should measure 0.5 volt or less.
^ When selector lever position is "D," voltage should measure 0.5 volt or less.
^ When selector lever position is "3," voltage should measure 0.5 volt or less.
^ When selector lever position is "2," voltage should measure 0.5 volt or less.
^ When selector lever position is "L," voltage should measure battery positive voltage.
Q: Is the measured voltage within the specified range?
YES: Go to Step 18.
NO: Turn the ignition switch to the "LOCK" (OFF) position. Go to Step 17.

STEP 17. Check harness for open circuit or short circuit to ground between Park/Neutral position switch connector B16 terminal 6 and PCM connector C-114 terminal 110.








Q: Is the harness wire in good condition?
YES: Go to Step 18.
NO: Repair or replace the harness wire.

STEP 18. Using scan tool MB991502, check data list item 61: Park/Neutral Position Switch.

CAUTION: To prevent damage to scan tool MB991502, always turn the ignition switch to the "LOCK" (OFF) position before connecting or disconnecting scan tool MB991502.





1. Connect scan tool MB991502 to the data link connector.
2. Turn the ignition switch to the "ON" position.
3. Set scan tool MB991502 to data reading mode for item 61: Park/Neutral Position Switch.
^ Move the selector lever to "P," "R," "N," "D," "3," "2," "L" positions and confirm that the selected selector lever positions match the positions shown on scan tool MB991502.
4. Turn the ignition switch to the "LOCK" (OFF) position.
Q: Is the switch operating properly?
YES: It can be assumed that this malfunction is intermittent.
NO: Replace the PCM.

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