P2101 is a general OBD2 trouble code. It has the same meaning for the Cadillac STS as it would any other vehicle. It is typically caused by wiring issues at the throttle actuator, or a bad throttle actuator itself.
P2101 Definition: Throttle Actuator “A” Control Motor – Circuit Range/Performance
Throttle Actuator “A” Control Motor Circuit (TAC for Short)
Your STS does not use a physical throttle cable. It is controlled by the PCM. A signal is relayed from the gas pedal to the PCM telling it how much of torque you are requesting. It will then control the throttle using a motor that opens and closes the throttle blade.
The advantage of this is that it’ll bring the torque in a bit slower than a traditional gas pedal. This saves a lot of wear and tear on the engine.
The throttle actuator does not necessarily have to be located on the throttle body itself. You can find it on the engine, firewall, or wheel wells.
Circuit Range/Performance
There are a lot of fail-safes built into the electronic throttle control system. P2101 means that your STS’s PCM has noticed a discrepancy between the throttle input and the actual throttle position.
P2101 indicates that the throttle is not opening and closing in the way that you, the driver, are requesting it to. The signal is, therefore, “out of range.”
Cadillac STS: P2101 Symptoms
Limp Mode
P2101 will most likely put the vehicle in limp/failsafe mode. This limits throttle response. Depending on the make, model, year, and engine, the amount of throttle you get will vary.
Check Engine Light
P2101 can sometimes appear with other codes but will often appear by itself. It is likely that P2106 will appear too. This is letting you know that your STS is in limp mode.
Improper Idle Speed
You may get a higher idle speed and no throttle response. This higher idle speed will allow your STS to be moved out of the way, but that’s about it. Different engines
P2101 Causes
- Wiring problem with the throttle control system, particularly where the actuator plugs into the harness.
- Bad Throttle Actuator
- PCM problem
P2101 Diagnosis: Cadillac STS
The good news with P2101 is that there’s not much to test and inspect that can throw this code.
The most common reasons that P2101 has appeared are wiring issues or a bad throttle actuator. Here’s how to go about fixing P2101 in your Cadillac STS.
1. Check the Wiring on Throttle Actuator
The first thing you should do is find the Throttle Actuator “A.” Depending on the model year and engine in your STS, it could be in several places. It can be on the firewall, fender, behind the firewall, or the engine.
Inspect the entire harness to make sure that there is no damage (think frayed or burnt wires, loose connections, etc…). Look particularly close anywhere that the wiring harness is close to the metal. If there is some form of damage, you’re going to need to replace the part of the harness in question.
Inspect where the harness plugs into your STS’s Throttle Actuator. Check it for corrosion. Use an electrical contact cleaner to clean any terminals and contacts that need it. This is a prevalent cause of P2101.
If there was damage, replace or repair the harness as needed. Then, use your OBD2 scanner to clear P2101. Next, fire Fire the engine up and blip the throttle. If it’s responding again, you’re done.
If there did not appear to be any damage, go ahead and move on to testing the Throttle Actuator.
2. Test Throttle Actuator “A”
Most throttle actuator motors use two wires. Use a multimeter to determine if there is an open or short. If there is, go ahead and replace it.
If it’s not open or short, check the power supply to the throttle actuator. Confirm that it has the proper voltage. You can use a scan tool to command the Throttle Actuator while using a test light to determine if it’s getting sent the signal. If the test light doesn’t come on, it indicates that there is a wiring problem.
Try jiggling your STS’s wiring with the test light connected to the power wire and see if it flickers. That would indicate an intermittent wiring problem. Next, start lightly jiggling different parts of the harness until you find exactly where it is coming from.
3. PCM
It is doubtful that there is an issue with the PCM, but it’s not improbable.
Conclusion
You’ll likely be chasing a wiring problem or a bad throttle actuator to clear P2101.
If there are any other codes, you can cross-reference them with this one and see if there are overlapping causes.
You can look to see if there are any TSB’s (Technical Service Bulletins) related to the throttle actuator for your year Cadillac STS. It just might save you some time in diagnosing P2101.