FAQ
TL;DR: Common culprit for Volvo FH13 JShift MID 130 PSID26 FMI7 is a cracked selector piston rod; fix held 3 years, ~PLN 700. “The crack was not visible until it cracked.” [Elektroda, DAMIAN124420, post #19666627]
Why it matters: This FAQ helps FH/J‑Shift owners diagnose cold-start air/braking symptoms and clear the persistent MID130 PSID26 FMI7 fault fast.
Quick Facts
- Code scope: MID130 PSID26 FMI7 points to the gears 2/3 engagement system in the Transmission Control Unit. [Elektroda, Cobrat, post #16928361]
- Cold-start telltales: air hissing at the gearbox and error that clears after an ignition cycle. [Elektroda, DAMIAN124420, post #16929489]
- Drivability: throttle can cut on 5→6 shift; one edge case held 10th gear until restart. [Elektroda, AdamRogulski, post #19618864]
- Proven fix: cracked piston rod; clean the selector cartridge and replace O‑rings; ~PLN 700; 3 years OK. [Elektroda, DAMIAN124420, post #19666627]
- Tip: air from the box vent suggests pistons under the electronics require repair. [Elektroda, stanisławpiotr, post #17029909]
What does MID 130 PSID 26 FMI 7 mean on a Volvo FH13 JShift?
It identifies a Transmission Control Unit fault in the gears 2/3 engagement system. The code narrows diagnosis to the selector and related pneumatics. Start with the selector pack and its pistons, seals, and control coils. Check for air leaks and cold-shift behavior. [Elektroda, Cobrat, post #16928361]
Why does the fault show up only when the transmission is cold?
Cold seals and a marginal crack can leak more air until temperatures rise. The OP reported hissing air from the gearbox and a fault that vanished after restarting once warm. This pattern points to selector leakage or a cracked actuator component aggravated by low temperatures. [Elektroda, DAMIAN124420, post #16929489]
I hear air escaping near the gearbox—what should I check first?
Listen at the gearbox vent. If air leaks there, focus on the selector pistons located beneath the electronics. Rebuild or repair that piston set and inspect the actuator rod for damage. “If you can hear the air from the box vent, the pistons... for repair.” [Elektroda, stanisławpiotr, post #17029909]
The truck cuts throttle during the 5→6 shift and then drives fine after a restart. What’s happening?
That pattern matches a selector or pneumatic issue causing temporary loss of shift control. One user replaced multiple parts without resolution, and the symptom cleared only after cycling ignition. An edge case held 10th gear at a stop before a restart fixed it. [Elektroda, AdamRogulski, post #19618864]
What actually fixed the recurring MID130 PSID26 FMI7 fault in this thread?
A cracked piston rod on the selector roller was the root cause. The repair included cleaning the entire cartridge and fitting new O‑rings. After this, the truck ran fault‑free. “The crack was in such a place that it was not visible until it cracked.” [Elektroda, DAMIAN124420, post #19666627]
How much did the successful fix cost and how long did it last?
Approximate outlay was PLN 700 for parts and service around the selector cartridge. The poster reports three years of trouble‑free operation after repair. That durability strongly implicates the cracked rod and sealing as the true fault path. This provides a practical target repair. [Elektroda, DAMIAN124420, post #19666627]
How do I confirm a cracked piston rod in the selector pack?
- Remove the selector cartridge and clean it thoroughly.
- Inspect the piston rod on the roller for hairline cracks under good light.
- Replace the rod if cracked, and fit new O‑rings; reassemble and test.
This exact sequence resolved the fault for the OP. [Elektroda, DAMIAN124420, post #19666627]
Will replacing gaskets, the accelerator pedal, or the EBS cassette fix this code?
Not necessarily. One owner replaced rectangular gaskets, all selector seals, the accelerator pedal, the EBS module, and the selector tape—spending about PLN 8,000—without a cure. The root cause remained in the selector’s mechanicals until addressed. Diagnose before shotgun parts replacement. [Elektroda, AdamRogulski, post #19618864]
The fault disappears after I cycle the ignition. Is that a known behavior?
Yes. Several reports show the error clears after switching off and on, then returns under specific shifts while cold. This suggests a marginal leak or crack that self‑seals once warm or repressurized. Plan a mechanical inspection rather than relying on resets. [Elektroda, DAMIAN124420, post #17030367]
Where are the pistons and coils everyone mentions?
They sit beneath the selector electronics on the gearbox. Coils control the pistons that route air for gear engagement. If air leaks through this section, the pistons or their seals likely need service. Prioritize this assembly when MID130 PSID26 FMI7 appears. [Elektroda, stanisławpiotr, post #17029909]
Do I need calibration after clutch or selector work?
Yes. Ensure selector regeneration and clutch procedures include calibration. One responder specifically asked whether the calibration was completed after parts work. Without correct calibration, shifts can misbehave and mask underlying mechanical issues. Confirm procedures with Volvo diagnostics. [Elektroda, Cobrat, post #16928361]
What symptoms point to a sealing problem versus electronics?
Air hissing, faults on cold start, and improvement as the drivetrain warms suggest sealing or mechanical faults. Electronics faults rarely improve with temperature or simple restarts. “Auto whistle chauffeur...” hints the noise is mechanical, not the ECU. Investigate seals and the piston rod first. [Elektroda, trucktech, post #18386673]
Could a cracked rod be invisible until it finally fails?
Yes. The OP reported the crack was hidden until it fully fractured. After the break, the cause became obvious during teardown. This explains intermittent behavior before failure and the cold‑only pattern many owners observe. Quote: “not visible until it cracked.” [Elektroda, DAMIAN124420, post #19666627]
What’s a practical first diagnostic step without special tools?
Listen for air at the gearbox vent right after a cold start. If you hear a hiss, focus on the selector pistons under the electronics and plan a cartridge service. This simple check can save time and parts costs. [Elektroda, stanisławpiotr, post #17029909]
