P1123
ChryslerThe computer sees the throttle position sensor reading higher than it should be, even when you're just idling or barely touching the pedal. It's in range, but still out of whack for what the engine's doing.
Medium SeverityThis code means the Throttle Position Sensor is lying to the computer, saying the throttle plate is open more than it actually is. It messes with your idle and how the engine takes the gas.
⚠️ Before You Begin (Safety First)
Before you start poking around, disconnect the battery's negative terminal. Don't go sticking your fingers where they don't belong in moving parts or hot spots. Electrical work can bite you if you're not careful. Use eye protection. Common sense stuff.
Common Symptoms
- Engine idles too high.
- Rough or erratic idle.
- Poor throttle response. Feels sluggish.
- Cruise control might not work right.
- Check Engine Light is on, obviously.
- Transmission might shift funny.
Common Causes
- Bad Throttle Position Sensor. They just go bad.
- Corrosion or damage in the TPS connector. Gets dirty.
- Wiring problems to the TPS. Frayed wires, open circuits.
- Throttle body stuck slightly open or gummed up.
- PCM issue, but that's rare for this code.
Frequently reported on: 2005 Dodge Grand Caravan, 2008 Chrysler 300, 2010 Jeep Wrangler, 2007 Dodge Ram 1500, 2006 Chrysler Pacifica
Diagnostic Steps
- Check the TPS connector. Make sure it's clean and tight.
- Inspect the wiring harness for damage. Look for rubs or breaks.
- With the key on, engine off, check TPS voltage at idle. Should be low, usually under 1 volt. Sweep the throttle slowly; voltage should climb smoothly to near 5 volts at wide open throttle.
- Clean the throttle body if it's gummed up. Make sure the plate moves free.
- Replace the Throttle Position Sensor. It's usually held on with a couple of screws.
- Clear the code and take it for a drive.
👨🔧 When to Call a Professional
If you've swapped the sensor and the code still comes back, or if the wiring looks chewed up, take it to a shop. Don't chase ghosts in the wiring harness if you're not set up for it. Sometimes it's a computer problem, and that's beyond most driveway fixes.
Commonly Asked Questions
Can I drive with P1123?
Yeah, probably. But it'll run like crap. High idle, bad mileage. Don't expect it to fix itself.
Is it always the TPS?
Most of the time. It's the first thing you check. But wiring issues or a dirty throttle body can trick it.
What's a TPS do anyway?
It tells the computer how much gas you're trying to give it. Without it, the computer doesn't know what to do with the fuel and air.
How do I test the TPS?
Use a multimeter. Key on, engine off. Check the voltage signal. Starts low, should go smooth up to 5 volts as you open the throttle by hand.
Can I adjust the TPS?
Most modern ones, no. They're fixed. If it's old and has slots, maybe. But usually, you just replace it.