I don’t see many of the “Tin Can” TCU’s they are a bit more reliable then the Plastic Sealed Daihatsu 89530-87507 86410-2750 TCU’s. But they to are also prone to failure due to leaking capacitors.
Daihatsu Hijet 89530-87509 / 89530-87511 Transmission Control Unit (TCU) Repair
This Case is a moderate case, (Top Right Corner) This Will require a little bit of corrosion clean up and some trace repair. I think this one has a good chance of recovery.
Capacitor Leakage and Corrosion
Another Area Of Capacitor Leakage C5 By the Transistors, this is Very mild and the electrolytic leakage appears to not have migrated under the MCU or Corroded away the the transistors you can see it started to attack them.
The Traces of TR12, TR1, TR10, TR8 “L6” (2SC1623) should be inspected at the pad for corrosion. In this case TR1, TR10, TR12 had broken connections and Corrosion Starting on ZD2
These units often require as much time or in some cases, even more to repair than their plastic-encased counterparts that must be physically cut open. This is largely due to the extent of electrolytic corrosion, which can be quite severe and labor-intensive to remediate.
The most common issues observed include:
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Electrolytic Capacitor Leakage – The primary issue, typically resulting in localized corrosion and conductive residue that must be thoroughly cleaned and neutralized.
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Corroded Traces and Vias – Particularly beneath the EL6004EM and the MCU where electrolyte intrusion from failed capacitors corroders the via and traces
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Corroded, Cracked, or Cold Solder Joints / Traces on the MCU. If the electrolytic cap next to the MCU leaks it will corrode the traces requiring MCU removal repair of traces and via’s.
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Failed Transistors – In more severe cases, shorted, Corroded or thermally damaged transistors are observed. If visibly burnt, it usually indicates catastrophic failure of the MCU, rendering the unit irreparable as this is a Proprietary Marked Chip. If they are just corroded pad and trace repair is required.
Some Photos of this Unit.
Primary Corrosion (Area is Wet With Flux) All the black is Corrosion.
Under IC2 a EL6004EM The Via’s have completely corroded away and will need to be repaired.
Main Ground Plane Area By the Capacitors Needs Repaird.
Cleaning the Corrosion, This is a must you need to use a fiberglass pen and clean.
You Will Notice the pads have been corroded away and have no contact or minimal contact with their traces.
If There is black on the traces the solder mask and conformal coating must be removed to clean this or it will continue to corrode the copper.
Bottom of the board vias cleaned.
After Solder Mask Removal area it tined with solder this is the first round, 2nd round gets whats missed.
Repair the vias by filling with a wire, Note: this is a 4 layer PCB the only inner traces I am aware of are at the MCU (IC1) I would like to get one of these and sand it down to map them out but finding one Beyond economical repair that not overly corroded can be used for this would be difficult. X-ray would be ideal for this but there is no one around here with one that is reasonable.
Replaced Parts
C7 .01uf 50V Ceramic (Check this capacitor for deterioration and cracks)
C5 / C4 10uf 16V (Note: these should be upgraded to 25V for extended life)
C3 3.3uf 50V (Leaked)
C2 1uf 50V (Leaked)
C1 100Uf 50V (Leaked)
R1 47K 1/8 Watt Carbon (Leads Corroded)
R2 2.7K 1/8 Watt Carbon (Leads Corroded)
R4 10K (Corroded)
Some photos of the repaired unit they are not pretty but all connections have good contact and corroded copper areas have solder build up.
Transistor pad and trace repair. Be sure to remove the transistors to clean underneath them. Repaired Traces/Pads At Transistors small magnet wire for jumpers work for the heavily corroded traces with large gaps otherwise a small bridge works. Check continuity with a DMM.
Daihatsu “Tin Can” TCU Repair Pricing
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Minimum Corrosion Repair: $250.00 + parts and return shipping
(Covers standard capacitor leakage and up to 1–3 trace/pad repairs) -
Moderate Corrosion Repair: $350.00 + parts and return shipping
(Applies to units with 4 or more trace/pad repairs due to leakage or oxidation. Example shown in this post) -
Severe Corrosion Repair: (Major reconstruction leakage at or under MCU)
Flat rate for moderate repair + $135/hour for board reconstruction (up to 2 hours max) -
Non-Repairable Assessment Fee: $135.00
(If there is excessive damage and it requires more than 2 hours of reconstruction, or Bad custom Parts, the unit will be deemed non-repairable and this bench fee will apply)
Repair Evaluation Options
You may either:
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Send the TCU in for evaluation, and I will provide a repair quote upon inspection.
– OR –
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Email clear photos of the internal PCB for a preliminary assessment. Most units can be opened by carefully bending the tabs on the bottom side and lifting off the cover. there are no bonding wires in this unit that can be damaged.
Please send photos or inquiries to: tcu @ rhine-labs . com
Last Updated on June 16, 2025 by Steven Rhine