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 mild 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 Area By the Capacitors.
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 with their traces.
On this TCU
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 0805 (Corroded)
This TCU Repair is in Progress.
I Normally charge the same for the repair of these as the sealed plastic ones + Parts and shipping. If the corrosion is a mild case. If the corrosion is more then a mild case I will let you know. There are many variation of these and I cannot keep all parts in-stock so sometimes parts need to be ordered. (Some parts IC2 and IC1 the MCU are Unobtainable)
Basic Repair Mild Corrosion $250 + parts
Medium Corrosion Flat Repair + $135Hr for Reconstruction up to 2 Hours.
Bench Fee For Heavily Corroded “Not Repairable” $135 if it takes over 2 hours it will be deemed non repairable.
Last Updated on June 12, 2025 by Steven Rhine