P1122
FordThrottle Position (TP) Sensor Circuit Intermittent Low Voltage
Medium SeverityThis code means the Throttle Position (TP) sensor isn't sending a steady voltage signal, it's dropping out. When that happens, the computer doesn't know how much throttle you're giving it, so the engine gets confused and won't run right.
⚠️ Before You Begin (Safety First)
Always disconnect the battery before messing with electrical parts. Watch out for hot engine parts and moving belts if the engine is running. Don't touch the throttle body while the engine is running unless you know what you're doing.
Common Symptoms
- Rough idle
- Engine hesitation or stumbling during acceleration
- Poor throttle response
- Check Engine Light is on
- Engine may go into "limp mode"
- Stalling at idle
Common Causes
- Faulty Throttle Position (TP) sensor
- Corroded or loose wiring harness connector at the TP sensor
- Damaged wiring to the TP sensor
- Intermittent short in the TP sensor circuit
- Rarely, a bad Powertrain Control Module (PCM)
Frequently reported on: 1998-2004 Ford F-150, 1996-2003 Ford Taurus, 1997-2004 Ford Expedition, 2000-2005 Ford Focus, 1996-2001 Ford Explorer
Diagnostic Steps
- Inspect the TP sensor connector for corrosion or damage.
- Check the wiring harness leading to the TP sensor for any signs of fraying or shorts.
- Unplug the TP sensor and check for bent or dirty pins.
- Using a multimeter, test the TP sensor voltage output at different throttle positions.
- If the sensor voltage is erratic or consistently low, replace the TP sensor.
- Clear the code and test drive the vehicle.
👨🔧 When to Call a Professional
If you've checked the wiring and swapped the sensor and the problem's still there, or if you don't have a multimeter to test the circuit, take it to someone who does. Could be a PCM issue then, and that's not a DIY job.
Commonly Asked Questions
Can I drive with a P1122 code?
You can, but it's going to run rough. Don't expect smooth acceleration or good mileage. Best to fix it quick before it strands you.
How do I test the Throttle Position Sensor?
Get a multimeter. Key on, engine off. Probe the signal wire and ground while slowly opening the throttle by hand. You should see a smooth, increasing voltage from around 0.5V to 4.5V. If it jumps around or drops out, it's bad.
Is a P1122 always the sensor?
Most of the time, yeah. But don't just throw parts at it. Check the connector and wiring first. Could be a chafed wire causing that intermittent signal drop.
What if replacing the sensor doesn't fix it?
Then you've got a wiring problem between the sensor and the PCM, or worse, a bad PCM. That's when you need a shop with advanced diagnostic gear.
What's "limp mode"?
That's when the computer knows something's wrong and it limits engine power and speed to prevent damage. You'll notice reduced acceleration and often a speed limit.