Code P1501: Why Is Your Car Stalling or Shifting Rough?

Check Engine Light on? If your scanner shows P1501, you are likely dealing with a sensor that controls how your car moves or how it sits still. Like its neighbor P1500, this is a manufacturer-specific code, meaning a Ford treats it very differently than a Mitsubishi.

Decoding P1501: Speed vs. Idle

Depending on what you drive, P1501 usually points to one of two major headaches:

🏎️ Ford / Mazda

"Vehicle Speed Sensor (VSS) Out of Range"

The computer thinks the car is moving faster (or slower) than is physically possible based on other data. This often puts the car in "Limp Mode" or causes harsh transmission shifts.

🛑 Mitsubishi

"Idle Speed Control (ISC) Valve Malfunction"

The system that keeps your engine running at red lights is failing. Your RPMs might dip dangerously low, or the engine might stall completely when you stop.

How to Diagnose P1501 with iCarsoft CR Ultra P

Generic code readers are useless here because they can't command the sensors to test them. You need the iCarsoft CR Ultra P to perform "Active Tests."

1. The "Idle Relearn" Test (Mitsubishi/Subaru)

If your car is stalling, the Idle Air Control (IAC) valve might be stuck with carbon, or it just lost its memory.

Step 1: Connect the CR Ultra P and access the Powertrain module.
Step 2: View Live Data for "Target Idle RPM" vs. "Actual Idle RPM." If there is a big gap, there is a problem.
Step 3: Clean the throttle body, then use the CR Ultra P to run an "Idle Air Volume Learn" reset. This forces the ECU to re-calibrate the idle position.

2. The "VSS" Data Check (Ford/Mazda)

If you suspect a bad speed sensor:

Step 1: Select "Vehicle Speed" in the Live Data stream.
Step 2: Drive safely. If the graph shows spikes (e.g., jumping from 30mph to 100mph instantly), the sensor is glitching (shorting out).
Step 3: The CR Ultra P can also scan the ABS module simultaneously. If the ABS wheel speed sensors read correctly but the Transmission speed sensor doesn't, you've pinpointed the exact faulty part.

Common Questions About P1501

Can I drive with a P1501 code?

It's risky. On a Ford, your transmission may shift violently, causing internal damage. On a Mitsubishi, the car might stall in the middle of an intersection, which is a safety hazard.

Where is the Idle Control Valve located?

It is usually mounted directly on the throttle body. Over time, it gets clogged with carbon buildup. Sometimes a simple cleaning clears the P1501 code, but you will still need a scanner to reset the idle values.