What it means
Intermediate shaft speed sensor B signal voltage above the upper limit. Wiring faults of this kind typically come from chafing, water ingress at connector seals, or pin push-back — a wiggle test on the harness while the code is active often confirms the location.
At a glance
- Usually lights the check-engine light
How it works
Intermediate shaft speed sensor B reports the speed of a second intermediate shaft or sensing point, where fitted. The transmission control module sets P07C8 when sensor B's signal voltage exceeds its expected upper limit, which can result from a signal wire shorted to reference voltage or another powered circuit.
Common causes
Most likely first.
- Signal wire shorted to reference voltage
- Connector pins corroded - high contact resistance
- Supply wire pinched against B+ source
Symptoms
- Check engine or transmission warning light on
- Harsh, delayed, or missing shifts
- Possible limp mode (locked in one gear)
- Slipping or shuddering during gear changes
How to diagnose it
- Record freeze-frame data and check live data specifically for intermediate shaft speed sensor B to see whether its reading is implausible or fixed high when the fault occurs.
- Locate sensor B using vehicle service information, then inspect its connector and harness for moisture, corrosion, pushed-back pins, or wiring pinched against a reference or battery-voltage source.
- With the fault present, gently move the harness near sensor B while watching its live reading to locate an intermittent high signal.
- Use the vehicle wiring diagram to check whether sensor B's signal wire is shorted to its reference or another powered wire.
- If wiring and connections are sound, test sensor B and its supply and ground circuits against the manufacturer's specification.
Common fixes
- Repair a pinched or chafed wire that is feeding voltage into sensor B's signal circuit.
- Clean and secure corroded or loose sensor B connector terminals, and repair damaged seals.
- Repair a damaged connector pin or restore proper terminal contact.
- Replace intermediate shaft speed sensor B if it fails testing.
Can I keep driving?
If the vehicle shifts normally and only the warning light is on, drive cautiously and arrange diagnosis soon. Avoid towing and hard acceleration; incorrect shaft-speed data can cause harsh shifts, slipping, or a protective shift mode.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.