Field notes
Restoration guides, technical breakdowns and pump system know-how.
Evo VII–IX ACD/AYC Codes 45, 46, 81 and 82: What They Mean
Codes 45 and 46 are the pressure sensor, 81 the pump relay, 82 no pressure. How to read them and what to check first.
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ACD/AYC Pump Fluid: Type, Change and Maintenance (Evo VII–X)
ATF SP III, about one litre, reservoir in the boot. How to check it, when to change it, and the AYC diff oil mix-up.
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Service Required 4WD on the Evo X and Lancer Ralliart: What It Means and What to Do
What the Service Required 4WD warning means on the Evo X and Lancer Ralliart, what causes it and what to check first.
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Evo X Codes C161E and C161C: What They Mean and How to Fix Them
C161E is a pressure problem, C161C is electrical. What each code means, what causes it and how to diagnose it.
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ACD/AYC Pump Noise: Whining, Grinding and a Pump That Won't Stop
What a healthy ACD/AYC pump sounds like, and what whining, grinding or a pump that never stops tells you.
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How to Bleed the ACD/AYC System Without MUT-III
My lift method for bleeding the ACD/AYC system without MUT-III: preparation, the ACD stage, both AYC circuits, and when bleeding won't help.
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ACD Pump Restoration Process
What a full ACD/AYC pump rebuild involves, what gets replaced, and why bench testing under load is the stage that matters.
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ACD/AYC Pump Failure Symptoms: How to Tell Your Pump Is Dying
The first signs of a failing ACD/AYC pump, what they look like on the Evo VII–IX and Evo X, and how to tell the pump from a sensor or fluid fault.
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What is the ACD System and How Does It Work
How Mitsubishi's Active Center Differential works, which Lancer Evolution models actually have it, and why US-market cars differ.
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