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2006 Lexus GS300 P0606 and C1201 Codes Reappearing After ECM/PCM Replacement

Model: 2006 Lexus GS300 Fault Code: C1201 Posted: 2011-03-20 19:38

Hi everyone, I'm facing a recurring issue with my 2006 Lexus GS300 (GRS190 model) equipped with a 3GR V6 engine. The vehicle has accumulated approximately 92,000 km of mileage. The problem occurs when starting the car: the MIL (Malfunction Indicator Lamp), along with the VSC and TRC lights, illuminate intermittently. These warnings typically disappear after shutting off and restarting the vehicle, but they reappear frequently during operation. A diagnostic scan revealed two trouble codes: P0606 (ECM/PCM Processor Malfunction) and C1201 (Engine Control System Malfunction). According to the factory repair manual, replacing the ECM/PCM unit is the recommended solution. I replaced the first ECM/PCM with full reflash and programming, which initially resolved the issue. However, after about eight months of normal use, the same codes returned. I then replaced the second ECM/PCM unit—again following the repair manual's guidance—and inspected all wiring connections for faults, finding none. Despite this, when I started the vehicle today, both P0606 and C1201 reappeared upon startup. I'm now seeking advice on possible root causes beyond a faulty ECM/PCM. The vehicle is driven in consistently hot conditions (year-round temperatures around 100°F), with regular rainfall but no winter or freezing exposure. All roads are paved, so there's no off-road use. Any insights into alternative diagnostics or underlying system issues would be greatly appreciated. Thanks in advance for your help!

Related fault codes
C1201P0606
Comments (9)
Anonymous 2011-03-21 05:10

Where can I purchase a genuine ECM/PCM unit for my 2006 Lexus GS300, and who performs the programming and installation? Are there specific dealers or certified shops that offer this service?

Anonymous 2011-03-21 05:36

C1201 indicates an ABS inlet valve coil circuit short to ground. This fault can trigger the VSC and TRC warning lights. Please verify if the wiring from the left front wheel speed sensor to the ABS actuator (also known as the ABS & TRC & VSC Brake Assist Control Module) is intact.

Anonymous 2011-03-22 01:34

Hi Jeff, I purchased and had the second ECM/PCM unit installed at an authorized dealer. The vehicle is now out of warranty (original coverage was three years). While the technicians followed the repair manual steps, the issue persists even after replacement. The second PCM installation was free of charge but did not resolve the problem.

Anonymous 2011-03-22 01:42

Hi Mohawk, could you clarify which component to inspect for the ABS inlet valve coil circuit? Is it the ABS actuator or the left front wheel speed sensor? I haven't found detailed information about the ABS inlet valve coil in my service manual.

Anonymous 2011-03-22 08:26

Trace the wiring from the left front wheel speed sensor to the ABS actuator (commonly referred to as the ABS & TRC & VSC Brake Assist Control Module). The vehicle's service manual should include detailed circuit diagrams for this path.

Anonymous 2011-03-23 00:05

Thanks, Mohawk. I'll follow that wiring route and check for continuity or shorts. I’ll update everyone once I’ve completed the inspection and tested the system.

Anonymous 2011-05-31 19:43

P0606 may be caused by an oxygen sensor exhibiting abnormal impedance—specifically, one sensor failing to drop its resistance as expected during engine operation. The ECM interprets this as a potential internal fault. To diagnose: check the O2 sensor data list while running the engine and observe if any sensor fails to respond properly. Replace the faulty sensor, clear codes, and test drive. This issue may be linked to C1201.

Anonymous 2013-02-16 12:15

C1201 is a known issue on Lexus models when brake pads wear down and caliper pistons extend fully, causing brake fluid level to drop. The brake fluid sensor detects this drop and triggers the C1201 code if it remains active for over four seconds. Even without visible warning lights, the code may activate during uphill/downhill driving. To test: check the brake fluid level. If it's at minimum, add a small amount of fluid and reset the system to see if the code clears. For a permanent fix, replace worn brake pads, refill fluid to maximum level, then reset the code. This should resolve C1201 until the next brake service. Good luck—Expertmechanix Etobicoke

Anonymous 2013-02-16 12:55

Thanks for the input—but this issue has been ongoing for years. We're now dealing with more current problems that might be familiar to you.