FAQ
TL;DR: For Volvo FH (e.g., 2006–2011), MID 223 PSID 9 FMI 12 points to 3 likely causes and disables AUTO; “Generally, electrical installation needs to be checked, especially on ‘breaking’.” [Elektroda, Foxtrott, post #16814163]
Why it matters: This FAQ helps Volvo FH owners and techs quickly restore AUTO shifting by targeting the real fault, not the gearbox.
Quick Facts
- Symptom pattern: AUTO missing, manual works; sometimes forward only; engine/gearbox log no faults. [Elektroda, esterr, post #17820786]
- Common fault paths: selector wiring open/short, no sensor signal, or two sensors active. [Elektroda, Foxtrott, post #16814163]
- High-failure spots: cab-to-frame harness flex point and under-seat/selector connectors. [Elektroda, Piterr2212, post #17798685]
- Confirmed fixes include repairing or soldering broken wires under the driver’s seat. [Elektroda, Piterr2212, post #17798685]
What does MID 223 PSID 9 FMI 12 mean on a Volvo FH?
It flags a gear selector circuit fault. Typical causes are an open or short, missing sensor signal, or two selector sensors reading simultaneously. AUTO mode is inhibited until the circuit fault is cleared. “Generally, electrical installation needs to be checked, especially on ‘breaking’.” [Elektroda, Foxtrott, post #16814163]
Why does my FH only shift manually when this code appears?
The transmission controller disables AUTO if it detects a selector fault. Owners report manual still works, while AUTO vanishes, sometimes with forward-only movement logged by one case. This behavior comes directly from the selector error, not the gearbox. [Elektroda, darfur5, post #16814363]
Where does the wiring usually break?
A frequent failure point is the harness that flexes when you tilt the cab, at the cab-to-frame pass-through. Inspect the loom and strain-relief there for cracked insulation or pulled pins. Check continuity through the bend while moving the cab. [Elektroda, Foxtrott, post #16817219]
Which connectors should I check first?
Check two places: the plug directly under the selector and the multi-pin connector under the driver’s seat. Clean, reseat, and inspect for backed-out pins or stretched conductors at both locations. [Elektroda, esterr, post #17820786]
How do I fix the under-seat plug issue? (3 quick steps)
- Unplug the under-seat connector and inspect each pin and wire for breaks.
- Repair breaks; many owners solder and heat-shrink the conductors.
- Reseat the plug firmly and clear codes; test AUTO. [Elektroda, Piterr2212, post #17798685]
Could the joystick/selector itself be faulty?
Yes. The fault points to the selector side. A defective selector or its internal sensors can cause an open-circuit or dual-sensor state. Verify wiring first, then substitute a known-good selector if needed. “There is clearly a selector error, not a gearbox.” [Elektroda, Piterr2212, post #17798685]
Does swapping the K5 relay help with this code?
One owner tried swapping K5 relays with no change. That suggests the issue is not relay-related but in the selector wiring or sensors. Focus on connectors and harness integrity before relay diagnostics. [Elektroda, esterr, post #17820786]
How can I check if two selector sensors are active at once?
Monitor the selector’s signal lines while moving through positions. The controller flags a fault if two position sensors read active together. Inspect wiring for shorts between signal lines that could tie channels. [Elektroda, Anonymous, post #17245593]
Is the gearbox or engine at fault here?
Evidence from owners shows no engine or transmission faults when this code appears. The problem resides in the selector circuit, not internal gearbox mechanics. Fixing wiring restored normal operation. [Elektroda, esterr, post #17820786]
WD-40 made no difference—what next?
Cleaning alone may not solve fractured conductors. After cleaning, perform a tug test and continuity test on each selector wire. Repair any broken or high-resistance paths to restore AUTO. [Elektroda, esterr, post #17820786]
What do experienced techs recommend checking first?
Follow the selector circuit. Inspect for incorrect wiring, missing sensor signal, or simultaneous sensor activity. “Generally, electrical installation needs to be checked, especially on ‘breaking’.” Prioritize flexible sections and connectors. [Elektroda, Foxtrott, post #16814163]
Has anyone confirmed an under-seat cable break as the fix?
Yes. A recent owner reported a broken cable under the seat and fixed several more during repair. Restoring conductor integrity resolved the issue. [Elektroda, konradwantusiak, post #21770887]
My truck had the code, then everything worked again—should I still inspect it?
Yes. An intermittent manual-only episode was reported by another owner. That behavior indicates a marginal connection that could recur under vibration or cab tilting. Inspect and secure the wiring now. [Elektroda, pabloo88, post #17245005]
Do accelerator and brakes show faults with this error?
Owners noted accelerator response and brakes remained normal while the transmission stayed in manual. That supports a localized selector circuit issue rather than a broader system failure. [Elektroda, TomasAGC, post #16814135]
What basic tools help with this repair?
Use contact cleaner, small picks for terminals, heat-shrink, and a soldering iron if you choose permanent wire repair. Many owners report success after soldering damaged conductors. [Elektroda, Piterr2212, post #17798685]
