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2006 Cadillac CTS P201 P301 U0100 Codes: Causes and Fixes for Rough Idle and Flashing Check Engine Light

Model: 2006 Cadillac CTS Fault Code: U0100 Posted: 2014-02-24 07:06

This morning I started my 2006 Cadillac CTS and noticed the engine light was on, with a rough idle. While driving my wife to work, I observed that the engine light began flashing when I tried to accelerate. After dropping her off, I returned home and scanned the vehicle for diagnostic codes, which showed P201, P301, and U0100. I now understand these codes may be related, but I'm unsure why they appear together and what the root cause could be. The flashing check engine light is particularly concerning due to potential catalytic converter damage from over-fueling. I'm looking for insights into possible causes and practical fixes for this issue on my 2006 Cadillac CTS.

Related fault codes
U0100
Comments (5)
Anonymous 2014-02-24 08:29

The U0100 code may indicate an issue with an aftermarket remote starter. This type of system is known to trigger U codes, especially if there's a power supply problem or recent electrical work. The P201 and P301 codes suggest a fault in the circuit for the #1 fuel injector. A flashing check engine light is a serious warning—over-fueling from a faulty injector can lead to catalytic converter damage. Addressing this promptly is critical.

Anonymous 2014-02-24 14:30

I've reached out via private message to Kev2 for more insight. If anyone else has experienced similar issues with their 2006 Cadillac CTS, please share your experience or solutions—any help would be greatly appreciated.

Anonymous 2014-02-24 15:14

We encourage using the forum instead of private messages to get broader technical input. You mentioned having an aftermarket remote starter that was spliced into the #1 fuel injector circuit. Simply removing the fuse doesn't disconnect the wiring—try unplugging the fuel injector directly and check if the remote relay is still active. Having a detailed installation diagram for your remote system would help in safely disassembling it. Do not ignore the P301 code—it can lead to catalytic converter failure. Aftermarket starters are generally problematic; OEM-installed systems are rare exceptions.

Anonymous 2014-02-24 15:24

I agree—aftermarket remote starters are often unreliable and should be avoided. My car had a plug-in splice connected to the #1 injector. I removed the fuse for the starter and disconnected it from the injector. After clearing the codes, I restarted the engine—but the check engine light flashed again. Interestingly, when I give steady throttle, the light stops flashing and the engine shuts off. Also, removing the air filter from the intake manifold caused the car to stall—could this be related? It seems like a possible fuel delivery or airflow issue.

Anonymous 2014-02-24 15:50

The P201 code points to a wiring fault at the #1 fuel injector. To verify, unplug the injector and check for battery voltage on the white wire—there should be power, while the other wire should show no voltage and not be grounded. If this test fails, it may indicate an open circuit or poor connection. The next step would be to perform a resistance check on the injector using a multimeter, comparing readings with known good injectors.