richard.weiss
Member
Recently helped a fellow rider replace the Smart Control Unit (SCU) in his 2019.
That was a journey to say the least.
It was a perfect storm of problems starting with:
The critical mistake by the owner...followed by
...a dying battery...
…then procedures missing steps....
...then corrupting the ESL through too many attempts to pair a FOB with faulty procedure...
…then an intermittently faulty SCS...
…then an improperly repaired wire....
…then a VT55 that had not had firmware updated in years...
…then the VT55 didn’t work properly with the 2019 bike TPMS…
…then a dying battery in a TPMS...
…that bike needs a gremlin bell big time!
Root Cause:
Owner installed aftermarket air horn and connected it to the SCU horn circuit causing overload on A side of SCU.
"Second failure" after replacing the SCU the first time was thought to be a trunk light circuit failure but that was disproven. Found an exposed conductor on the horn circuit that was not properly repaired by the owner when he removed the aftermarket horn. That resultant short fried the replacement SCU.
So if you are counting, that is a total of three SCUs - the original, the 1st replacement, and the 2nd replacement....
Indications:
Horn would quit working, fuses 15 and/or 24 would blow, or trunk light would dim or go out. Note: Fuse 24 and trunk light circuit are on B side of SCU, horn and fuse 15 are on A side of SCU. SCU gets all its power for both sides via Fuse 24.
Thoughts:
Operations (How it works)
1) Majority of the circuits being used for aftermarket items are NOT on the actual CANBUS network. The CANBUS is the network between the 9 (MT) /11 (DCT) /12 (Airbag) computers onboard.
2) Many of the circuits controlled by the SCU are ground switched, not power switched.
3) These non-CANBUS circuits do have tight voltage and current tolerances that are designed or programmed into the SCU. (Example- all the aftermarket items that would not work on 2021’s but did work on the 2018-2020s). I assume the same tolerance constraints apply to the other computers onboard.
Failures and Indications
1) Even slightly overloading (too high an amp draw) on any circuit attached to the SCU may cause an SCU failure.
2) A trunk light issue may be the proverbial canary in the coal mine indicating a different issue(s) with the SCU and/or its other circuits. Your indications may vary.
3) Failures on the A side of the SCU can affect the B side of the SCU and vice versa.
4) Too many attempts to conduct the FOB pairing procedure may corrupt the security code in the ESL.
Replacement Observations and Lessons Learned (THE IMPORTANT STUFF)
1) You must have the original Smart Key (FOB)'s code. The code is stored in the ESL, not the SCU.
1) The overall SCU replacement process involves multiple procedures (SCU physical replacement and Smart Key registration, TPMS registration, ect).
2) SCU replacement procedure in Service Manual is missing steps. All other procedures are correct.
3) If you don't own a VT36 or VT37 TPMS tester and/or $15 SCS you will have to go to a dealership for some or all of the procedures. Repairs will be very expensive if paying out of pocket.
4) A VT55 TPMS tester is an older version of the VT36. The VT55 is a Honda authorized alternative to use during the TPMS registration procedure. However, it may not work.
5) An updated VT55 may or may not work effectively with the 2018+ TPMS. Your mileage my vary.
6) The VT36 and VT55 must be fully updated with the latest firmware before using
7) The SCS appears a bit unreliable - may have to perform registration procedures multiple times before it "takes". There may be other unidentified factors.
8) Battery must maintain full charge (12.3VDC or above) throughout all the procedures. Keep the bike on the trickle charger the whole time.
9) TPMS sensors that have weaker batteries may not "wake up" (inflate tire to 52psi for wake up) for registration and would also need replacing.
10) Worst case scenario for parts is one SCU, one Smart Key, and two TPMSs, about $850 before taxes.
SCU = ~$380
Smart Key = ~$110
TPMS = ~$175 each
That cost estimate does not include labor…..
DIY Cost Saver:
A DIYer that only has a SCS could replace the SCU and Smart Key (FOB), register the new Smart Key (FOB), then ride to a dealership that has a VT36 and have the dealership register the TPMSs.
FINAL LESSON: Connect all your aftermarket electrical accessories through a isolator
Hope this info is helpful.
Cheers
That was a journey to say the least.
It was a perfect storm of problems starting with:
The critical mistake by the owner...followed by
...a dying battery...
…then procedures missing steps....
...then corrupting the ESL through too many attempts to pair a FOB with faulty procedure...
…then an intermittently faulty SCS...
…then an improperly repaired wire....
…then a VT55 that had not had firmware updated in years...
…then the VT55 didn’t work properly with the 2019 bike TPMS…
…then a dying battery in a TPMS...
…that bike needs a gremlin bell big time!
Root Cause:
Owner installed aftermarket air horn and connected it to the SCU horn circuit causing overload on A side of SCU.
"Second failure" after replacing the SCU the first time was thought to be a trunk light circuit failure but that was disproven. Found an exposed conductor on the horn circuit that was not properly repaired by the owner when he removed the aftermarket horn. That resultant short fried the replacement SCU.
So if you are counting, that is a total of three SCUs - the original, the 1st replacement, and the 2nd replacement....
Indications:
Horn would quit working, fuses 15 and/or 24 would blow, or trunk light would dim or go out. Note: Fuse 24 and trunk light circuit are on B side of SCU, horn and fuse 15 are on A side of SCU. SCU gets all its power for both sides via Fuse 24.
Thoughts:
Operations (How it works)
1) Majority of the circuits being used for aftermarket items are NOT on the actual CANBUS network. The CANBUS is the network between the 9 (MT) /11 (DCT) /12 (Airbag) computers onboard.
2) Many of the circuits controlled by the SCU are ground switched, not power switched.
3) These non-CANBUS circuits do have tight voltage and current tolerances that are designed or programmed into the SCU. (Example- all the aftermarket items that would not work on 2021’s but did work on the 2018-2020s). I assume the same tolerance constraints apply to the other computers onboard.
Failures and Indications
1) Even slightly overloading (too high an amp draw) on any circuit attached to the SCU may cause an SCU failure.
2) A trunk light issue may be the proverbial canary in the coal mine indicating a different issue(s) with the SCU and/or its other circuits. Your indications may vary.
3) Failures on the A side of the SCU can affect the B side of the SCU and vice versa.
4) Too many attempts to conduct the FOB pairing procedure may corrupt the security code in the ESL.
Replacement Observations and Lessons Learned (THE IMPORTANT STUFF)
1) You must have the original Smart Key (FOB)'s code. The code is stored in the ESL, not the SCU.
1) The overall SCU replacement process involves multiple procedures (SCU physical replacement and Smart Key registration, TPMS registration, ect).
2) SCU replacement procedure in Service Manual is missing steps. All other procedures are correct.
3) If you don't own a VT36 or VT37 TPMS tester and/or $15 SCS you will have to go to a dealership for some or all of the procedures. Repairs will be very expensive if paying out of pocket.
4) A VT55 TPMS tester is an older version of the VT36. The VT55 is a Honda authorized alternative to use during the TPMS registration procedure. However, it may not work.
5) An updated VT55 may or may not work effectively with the 2018+ TPMS. Your mileage my vary.
6) The VT36 and VT55 must be fully updated with the latest firmware before using
7) The SCS appears a bit unreliable - may have to perform registration procedures multiple times before it "takes". There may be other unidentified factors.
8) Battery must maintain full charge (12.3VDC or above) throughout all the procedures. Keep the bike on the trickle charger the whole time.
9) TPMS sensors that have weaker batteries may not "wake up" (inflate tire to 52psi for wake up) for registration and would also need replacing.
10) Worst case scenario for parts is one SCU, one Smart Key, and two TPMSs, about $850 before taxes.
SCU = ~$380
Smart Key = ~$110
TPMS = ~$175 each
That cost estimate does not include labor…..
DIY Cost Saver:
A DIYer that only has a SCS could replace the SCU and Smart Key (FOB), register the new Smart Key (FOB), then ride to a dealership that has a VT36 and have the dealership register the TPMSs.
FINAL LESSON: Connect all your aftermarket electrical accessories through a isolator
Hope this info is helpful.
Cheers