Sensor Power Supply Low Voltage (Ford)
What does P1241 mean?
The P1241 code means the vehicle's onboard diagnostic system has detected: Sensor Power Supply Low Voltage (Ford). This is a critical severity code.
Common Symptoms
- Check Engine Light on
- Engine runs rough or misfires
- Poor throttle response
- Incorrect sensor readings on scan tool
- Intermittent stalling
Probable Causes (Ranked by Likelihood)
- Short to ground in 5-volt reference wiring Very High
- Internally shorted sensor dragging down reference High
- Corroded PCM connector pins on reference circuit Moderate
- Water intrusion in sensor connector Moderate
- PCM internal 5-volt regulator degradation Low
Step-by-Step Diagnostic Procedure
-
Measure 5-volt reference at PCM connector with sensors disconnected
-
Disconnect sensors one at a time while monitoring voltage
-
Inspect 5-volt reference connectors for water or corrosion
-
Check wiring between PCM and sensors for shorts to ground
-
Verify PCM output recovers when all sensors are unplugged
Frequently Asked Questions
How low does voltage have to be to trigger P1241?
The PCM typically sets P1241 when the 5-volt reference drops below approximately 4.0 volts. Normal operating voltage should be between 4.9 and 5.1 volts.
Can a bad TPS cause P1241?
Yes. A throttle position sensor with an internal short can drag the 5-volt reference low. Disconnecting the TPS to see if voltage recovers is a key diagnostic step.
Is P1241 always a wiring issue?
Not always. A failed sensor or internal PCM damage can also produce the same code. Systematic disconnection testing is essential for proper diagnosis.