P1634

DTC P1634 (47): MPI Module Signal Circuit Problem
1. Reset the MCM.
2. Turn the ignition switch OFF.
3. Turn the ignition switch ON (II).
Is DTC P1634 indicated?
YES-Go to step 4.
NO-Intermittent failure, system is OK at this time. Check for poor connections or loose terminals at the MPI module and at the MCM.
4. Turn the ignition switch OFF.
5. Turn the battery module switch OFF, and wait 5 minutes.
6. Remove the IPU lid, and make sure there is 30 V or less at the junction terminals.
7. Disconnect MCM connector A (31P).
8. Remove the PDU cover.
9. Disconnect the MPI module 16P connector.





10. Check for continuity between MCM connector terminal A18 and body ground.
Is there continuity?
YES-Repair short in the wire between the MPI module and the MCM (A18).
NO-Got to step 11.





11. Check for continuity between MCM connector, terminal A18 and MPI module 16P connector terminal No. 3.
Is there continuity?
YES-Go to step 12.
NO-Repair open in the wire between the MPI module and the MCM (A18).





12. Check for continuity between MPI module 16P connector terminals No. 2 and No. 10 and body ground individually.
Is there continuity?
YES-Go to step 13.
NO-Repair open in the wire between the MPI module and G101.
13. Reconnect MCM connector A (31P).
14. Turn the ignition switch ON (II).





15. Measure voltage between MCM relay 24P connector terminal No. 1 and body ground.
Is there battery voltage?
YES-Go to step 16.
NO-Go to step 19
16. Turn the ignition switch OFF.
17. Disconnect the negative cable from the 12 V battery.





18. Check for continuity between MCM relay 2 4P connector terminal No. 1 and MPI module 16P connector terminals No. 1 and No. 9 individually.
Is there continuity?
YES-Replace the MPI module).
NO-Repair open in the wire between the MPI module and MCM relay 2.
19. Check MCM relay 2.
Is the relay OK?
YES-Go to step 20.
NO-Replace MCM relay 2.
20. Reconnect the negative cable to the 12 V battery.
21. Measure voltage between MCM relay 24P connector terminal No. 2 and body ground.





Is there battery voltage?
YES-Go to step 25.
NO-Go to step 22.
22. Check the No. 2 IMA (10A) fuse.
Is the fuse OK?
YES-Repair open in the wire between the No. 2 IMA (10 A) fuse and MCM relay 2.
NO-Replace the No. 2 IMA (10 A) fuse, then go to step 23.
23. Turn the ignition switch OFF.





24. Check for continuity between MPI module 16P connector terminals No. 1 and No. 9 and body ground individually.
Is there continuity?
YES-Repair short in the wire between the MPI module and MCM relay 2.
NO-Repair short in the wire between the MPI module and the IPU module fan.
25. Turn the ignition switch ON (II).





26. Measure voltage between MCM connector terminal A4 and body ground.
Is there battery voltage?
YES-Update the MCM if it does not have the latest software, or substitute a known-good MCM, then recheck. If the symptom/indication goes away with a known-good MCM, replace the original MCM.
NO-Go to step 27.
27. Turn the ignition switch OFF.
28. Disconnect MCM connector A (31P).





29. Check for continuity between MCM relay 24P connector terminal No. 3 and MCM connector terminal A4.
Is there continuity?
YES-Go to step 30.
NO-Repair open in the wire between MCM relay 2 and the MCM (A4).
30. Reconnect MCM connector A (31P).
31. Turn the ignition switch ON (II).





32. Measure voltage between MCM relay 24P connector terminal No. 4 and body ground.
Is there battery voltage?
YES-Update the MCM if it does not have the latest software, or substitute a known-good MCM, then recheck. If the symptom/indication goes away with a known-good MCM, replace the original MCM.
NO-Test MCM relay 1.