FAQ
TL;DR: Volvo FH13 code MID 128 SID 85 FMI 5 often traces to the piston-cooling valve circuit; 1 blown fuse can trigger it. “Valve failure often blows the fuse.” [Elektroda, stanisławpiotr, post #17640748]
Why it matters: This FAQ helps Volvo FH13 owners and techs quickly diagnose and fix this recurring engine fault without guesswork.
Quick Facts
- Fault points: valve coil open circuit or coil short-to-ground in the piston-cooling valve circuit. [Elektroda, stanisławpiotr, post #16775109]
- Likely location: piston-cooling valve mounted on/near the engine filter block. [Elektroda, MACIEK_M, post #16771107]
- Protection: diagnosis often involves checking fuse F41 for a blown condition. [Elektroda, stanisławpiotr, post #17640864]
- If the solenoid was replaced and code persisted, inspect fuse and wiring next. [Elektroda, Anonymous, post #17640480]
- Symptom note: a failed valve can blow the fuse, leaving the code active. [Elektroda, stanisławpiotr, post #17640748]
What does Volvo fault MID 128 SID 85 FMI 5 actually mean?
It flags an electrical fault in the piston-cooling valve circuit. Typical failures are an open coil winding or a coil short to ground. That fault interrupts ECM control and logs the code. Replace or repair the affected valve or wiring to clear it. [Elektroda, stanisławpiotr, post #16775109]
Where is the piston-cooling valve on the FH13?
Technicians report this valve on or near the engine’s filter block. Inspect the harness and connector in that area for rub-through or corrosion. Look for oil contamination that can wick into the plug and raise resistance. Clean, reseat, and test continuity. [Elektroda, MACIEK_M, post #16771107]
Which fuse should I check for this fault?
Check fuse F41. A failed piston-cooling valve can blow this fuse and keep the code active. Test F41 with a meter, not just visually. Replace the fuse only after addressing the root cause to avoid repeat failure. [Elektroda, stanisławpiotr, post #17640864]
Can a bad valve really blow the fuse and cause the code?
Yes. An internally shorted coil draws excess current and blows the circuit fuse. The ECM then detects the open circuit and sets MID 128 SID 85 FMI 5. “Valve failure often blows the fuse.” Replace the faulty valve and restore power. [Elektroda, stanisławpiotr, post #17640748]
I replaced the solenoid but the error stayed—what now?
Confirm power and ground: test the fuse, harness continuity, and connector pins. A previously blown fuse or damaged wiring can leave the code latched. Clear the DTC after repairs and verify live status. Don’t assume the new part fixed supply issues. [Elektroda, Jacekm123123, post #17640089]
What’s the quick 3-step way to diagnose this code?
- Inspect and test fuse F41 with a meter.
- Check valve connector, harness, and coil resistance at the filter-block valve.
- Repair wiring or replace the valve, then clear the DTC and road test. [Elektroda, stanisławpiotr, post #17640864]
Does wiring matter if the solenoid tests OK?
Yes. A broken conductor or corroded pin creates an open circuit the ECM detects. Wiggle-test the harness near the filter block while monitoring continuity. Repair any damaged section and reseal connectors against oil ingress. [Elektroda, Anonymous, post #17640480]
Could a second (vertical) solenoid be the issue instead?
If F41 and wiring are good, another valve on that assembly might be faulty. However, the cited code targets the piston-cooling valve circuit. Test each coil on that block and compare readings before replacing parts. [Elektroda, stanisławpiotr, post #16775109]
What is an FMI and how does FMI 5 guide the fix?
Failure Mode Identifier (FMI) describes the fault type. FMI 5 indicates current below normal or open circuit. That points to a blown fuse, broken wire, or open coil. Prioritize power and continuity checks before component swaps. [Elektroda, stanisławpiotr, post #16775109]
What is MID 128 in Volvo diagnostics?
MID identifies the controller; MID 128 refers to the engine control module. A SID then points to a subsystem like the piston-cooling valve. Use this map to focus testing on the correct circuit first. [Elektroda, stanisławpiotr, post #16775109]
What’s a piston-cooling valve and why does it matter?
It controls oil jets that cool the pistons under load. Electrical failure disables control and may risk thermal stress. Fixing the circuit restores commanded cooling and prevents repeat DTCs. [Elektroda, MACIEK_M, post #16771107]
How common is a fuse-related cause for this code?
Forum experience indicates it’s frequent when the coil shorts. One expert noted that valve failure often blows the fuse. Treat F41 testing as a first step to avoid unnecessary parts. [Elektroda, stanisławpiotr, post #17640748]
Edge case: the fuses check out—what could still be wrong?
A partially shorted coil may pass a static fuse check yet misbehave hot. Substitute a known-good valve or measure coil resistance warm. Replace if readings drift out of spec or the code returns. [Elektroda, stanisławpiotr, post #16775109]
Will clearing the code without repairs help?
No. If power or the coil is still faulty, the ECM will re-log the DTC immediately. Fix the electrical cause first, then clear and confirm. [Elektroda, Anonymous, post #17640480]
Any tip to avoid repeat failures after repair?
Secure the harness away from sharp edges near the filter block. Clean and reseal connectors to prevent oil wicking and corrosion that lead to opens. [Elektroda, MACIEK_M, post #16771107]
