MID 130 PSID 27 – Clutch system

Contents

Before starting, we need to understand how the TECU knows where the clutch is and how it interprets the clutch position sensor signal. When fitting a new clutch, we calibrate the system. The calibration measures the fully engaged position, the fully disengaged position, the travel distance of the clutch cylinder and the time taken to reach these values.

After calibration, a value is stored, the “X1” value. This becomes the default resting fully engaged value. It is measured in millimeters. A healthy I-Shift clutch should have an X1 value of approximately 25.7mm.

Because this is a push type clutch, the thicker the clutch plate is, the higher the X1 value will be. This is because the pressure plate fingers move inward (toward the engine), and because the clutch cylinder is not spring loaded, it simply stops moving back when the pressure plate fingers stop pushing it. A thicker clutch plate results in the clutch cylinder resting further out (closer to the engine) and thus the higher X1 value.

As the clutch wears, it gets thinner, and because it’s a push type, the pressure plate fingers move outward (toward the transmission) pushing the clutch cylinder further back reducing the X1 value.

Performing a Clutch wear check test with Tech Tool, will show a vertical line along a horizontal line, marked 25.7 (or whatever the calibrated value was), this is the X1 value, and ball along the horizontal line with a less value, this is known as the X2 value. The TECU constantly monitors these 2 values and adjusts how much it needs to activate the clutch control valve accordingly and automatically.

MID 130 PSID 27 FMI 0 – Value too high

💭 Understanding the DTC:

According to Volvo’s service manual this DTC represents “Unintentional disengagement of the clutch”. A yellow warning “Check transmission at next stop” is displayed on the instrument cluster.

Essentially, the DTC is telling us that the Clutch control valve is leaking on the disengagement solenoid, fast or slow, constantly supplying air to the clutch cylinder. As a result the clutch is being disengaged unintentionally and the TECU needs to activate the engagement solenoids repeatedly to keep the clutch engaged.

❔ Why this FMI 0 (Value too high):

TECU expects the clutch cylinder to be in its resting position when fully engaged, but because the clutch is being disengaged by a leaky solenoid valve, the TECU sees the X1 / X2 is greater than expected. However, no matter how much the TECU tries to engage the clutch, the leaky solenoid keeps applying air pressure to the cylinder pushing it away from its resting value. Once the TECU realises that the clutch cylinder is not returning to its resting position, it logs the DTC FMI 0.

🧪 Test: Tech Tool > Test > Transmission > PWM Valves Clutch, Test > Leak test

⚠Warning: Before disconnecting any components, turn off the ignition to avoid unnecessary new DTC’s❗

✔ Solution:

Step 1: Replace the Clutch control valve.

Step 2: Run clutch and transmission calibration as a security measure

MID 130 PSID 27 FMI 1 – Value too low

Basically a mirror image of the above fault code, Unintentional engagement of the clutch. This DTC is logged when the TECU repeatedly has to activate the disengagement solenoids in the Clutch control valve to maintain the fully disengaged position. Unlike the above, this fault is caused by an air leak.

Possible causes include:

  • Clutch control valve
  • Clutch cylinder
  • Braided hose connecting the valve and the cylinder
  • Plastic connector for the braided hose on the clutch cylinder

🧪 Test: Tech Tool > Test > Transmission > PWM Valves Clutch, Test > Leak test

✔ Solution:

⚠Warning: Before disconnecting any components, turn off the ignition to avoid unnecessary new DTC’s❗

Step 1: Remove the clutch control valve and inspect the rubber gasket that seals against the bell housing. If it is damaged, replace with a new one (This is a service item available from Volvo) and run the test again. If the test still fails, proceed to Step 2.

Step 2: If the rubber gasket seems ok, fit another Clutch control valve (using a test unit if available) and run the test again. If the test still fails proceed to Step 3.

Step 3: Remove the transmission, the clutch cylinder and the braided hose.

Step 4: Fit the braided hose back to the clutch cylinder and submerge the entire unit in a bucket of water. Using a rubber tipped air gun, supply a small amount of air to the braided hose and watch for bubbles. If bubbles come out of the hose or fitting, inspect and replace as necessary. If bubbles come out the cylinder, replace the cylinder.

Step 5: Inspect the clutch for physical damage (while the transmission is out and you have access). Replace as necessary.

Step 6: Run clutch and transmission calibration

MID 130 PSID 27 FMI 7 – Mechanical system not responding properly

This DTC could be be anything really, from a leaky valve to a failed clutch. Simply put, the clutch is not operating as expected. Often accompanied with MID 130 PSID 28 FMI 7 – Transmission brake.

🧪 Test: Tech Tool > Test > Transmission > PWM Valves Clutch, Test > Leak test
🧪 Test: Tech Tool > Test > Transmission > PWM Valves Clutch, Test > Performance test
🧪 Test: Tech Tool > Test > Transmission > Clutch cylinder test

✔ Solution:

⚠Warning: Before disconnecting any components, turn off the ignition to avoid unnecessary new DTC’s❗

Step 1: Run the clutch tests to eliminate any potential issues with the clutch control system.

Step 2: Try another TECU, fit calibrate and test drive

Step 3: Remove transmission and inspect clutch system, and replace as necessary

Follow the steps as outlined above in MID 130 PSID 27 FMI 1.

MID 130 PSID 27 FMI 8 – Mechanical or electrical fault, Abnormal frequency, pulse width or period

Please refer to article MID 130 PSID 27 FMI 8 for a full explanation.

⚠Warning: Before disconnecting any components, turn off the ignition to avoid unnecessary new DTC’s❗

MID 130 PSID 27 FMI 11 – Unknown fault, Failure mode unidentifiable

This DTC is logged when the clutch is fully disengaged but there is some amount of drive detected. This can be caused by a warped flywheel, a sticky clutch plate or a seized pilot bearing.

Even though this fault is more than likely a mechanical issue with the clutch system, it is worth while running the same tests as above, plus the Input shaft speed sensor test.

🧪 Test: Tech Tool > Test > Transmission > PWM Valves Clutch, Test > Leak test
🧪 Test: Tech Tool > Test > Transmission > PWM Valves Clutch, Test > Performance test
🧪 Test: Tech Tool > Test > Transmission > Clutch cylinder test
🧪 Test: Tech Tool > Test > Transmission > Input shaft speed

✔ Solution:

⚠Warning: Before disconnecting any components, turn off the ignition to avoid unnecessary new DTC’s❗

Step 1: Run the clutch tests to eliminate any potential issues with the clutch control system.

Step 2: Place chocks in front of and behind the front wheels and release the parking brake. Lift one of the drive wheels and apply a small force to it to stop it rotating.

Step 3: Run the input shaft speed test. While the test is running try to hold the lifted drive wheel still. If the air is full, the clutch should be fully disengaged and the input shaft speed should be zero. If the wheel cannot be held, it means the input shaft is being rotated by the engine.

Step 4: Try another TECU, fit calibrate and test drive

Step 5: Remove the transmission and inspect the clutch, flywheel and pilot bearing. Replace as necessary.

MID 130 PSID 27 FMI 12 – Component fault

Conditions to set this DTC are a worn clutch or the clutch is slightly disengaged. This results in clutch slip. When the TECU detects that the clutch is slipping it logs the DTC and instructs the Engine ECU to limit torque. This is a preventative measure to ensure the truck can still move to a safe place for repairs.

Once again, we run all the clutch tests as outlined above, failing which, we need to remove the transmission to carry out a physical inspection of the clutch and replace if necessary.

🧪 Test: Tech Tool > Test > Transmission > PWM Valves Clutch, Test > Leak test
🧪 Test: Tech Tool > Test > Transmission > PWM Valves Clutch, Test > Performance test
🧪 Test: Tech Tool > Test > Transmission > Clutch cylinder test

✔ Solution:

⚠Warning: Before disconnecting any components, turn off the ignition to avoid unnecessary new DTC’s❗

Step 1: Run clutch tests as above

Step 2: Try another TECU, fit calibrate and test drive

Step 3: Remove transmission and inspect clutch system

MID 130 PSID 27 FMI 14 – Unknown fault, Special instructions

There is no special information relating to this DTC, however from my personal experience, this DTC is a result of a failed clutch. Quite often, it is accompanied with MID 130 PSID 28 FMI 7 – Transmission brake. Symptoms will include a Red warning on the instrument cluster and not able to select any gear. Sometimes the vehicle will get stuck in gear and starting will be inhibited.

As with all other clutch faults, i suggest running the tests as outlined above

🧪 Test: Tech Tool > Test > Transmission > PWM Valves Clutch, Test > Leak test
🧪 Test: Tech Tool > Test > Transmission > PWM Valves Clutch, Test > Performance test
🧪 Test: Tech Tool > Test > Transmission > Clutch cylinder test

✔ Solution:

⚠Warning: Before disconnecting any components, turn off the ignition to avoid unnecessary new DTC’s❗

Step 1: Run clutch tests as above

Step 2: Try another TECU, fit calibrate and test drive

Step 3: Remove transmission, inspect clutch system and transmission brake

Step 4: Replace as necessary, and calibrate