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Check VSC / C1201 + other codes

2K views 14 replies 2 participants last post by  01 SolarYellow 
#1 ·
Hei everyone, I hope you are doing great.

I bought my 2008 IS350 about a year ago and it has been awesome, aside from the Check VSC message on the instrument cluster. Allow me to further explain:

The "Check VSC" message surprisingly showed up for the first time immediately after filling up the gas tank with 95octane gas [the previous owner never mentioned nothing about this]. Aside from the Check VSC message on the instrument cluster there were no difference on my driving experience, everything felt normal, after like a month when I was driving my way to work and the car went to "Limp mode" [rpms wont go higher than 2000]. Since then I have tried several things, and the code always comeback. This is the order of the things I have tried after mainly exploring the web looking for solutions and considering other people experiences:

-Disconnected the battery = clears the code, but it randomly shows up again. As you may know, this actually clears everything, so this is no solution.
-Cleaned the MAF sensor with CRC Electric Cleaner
-Cleaned the Throttle Body with CRC Throttle Body and & Air-Intake Cleaner
-Replaced all 4 wheels Brake Pads with OEM ones
-Cleaned all 4 brake rotors and calipers with CRC Brakleen
-Replaced the fuel tank cap [I always fill up the tank up to its max point, no further, and close the cap after just one click, at the gas station]

The Check VSC message kept coming back, and as a consequence I continued getting into Limp mode randomly, so I decided to get myself the Bluetooth OBDII scanner. Scanning my car after getting into Limp mode I got C1201 together with P0504, P0175, P0172 and P1170, and I did the following:

-Replaced 6 spark plugs with OEM ones
-Disconnected and cleaned with CRC Electronic cleaner the 4 connectors that go into the Injector Driver ECU. Also cleaned/brushed the ground connections of this DCU.
-Replaced the PCV Valve
-Replaced the Fuel Filter Assy OEM
-Poured a 473ml bottle of Cataclean into may fuel tank when there was 1/4tank remaining [as per Cataclean indications]

So after the above the Check VSC kept coming back, and every now and then I have been going into Limp mode [I can get out of Limp mode by turning OFF the engine and starting the car back, but this is so annoying while daily driving as you might imagine].

Trying to go a little bit further I followed the advice of doing the "Zero Point Calibration" through Techstream [I got it from ebay] by selecting the ABS/VSC/TRAC "Utility", and executing the "Reset Memory", and then a "Test Mode". After these I cleared all DTCs, and after a day without any issues today I got the Check VSC message again. Doing a Health Check on all DCU I am getting C1201 together with P0175, P1170 and P0504 [I attach to this post the Freeze Frame Data Report from Techstream for each one of these].

The TIS Repair Manual suggests to replace the ECM, and if that does not do it then to replace the Skid Control DCU, but I have a hunch that this might not solve the issue after everything I have done. And seeing C1201 constantly together with the other codes I am starting to believe that it might just be a "consequence" DTC and not the root cause of whatever issue my car is having. Honestly, I have no expertise in Toyota/Lexus cars, and I cannot see how P0175 [System too rich], P1170 [Fuel Performance/Fuel Injector], or P0504 [Brake Switch A/B correlation] might be related to C1201 Check VSC and cause me to go to Limp Mode [unless this is some kind of engineered behavior to protect me as a driver from an accident by going to fast on the road], and all this time I have been troubleshooting the wrong code or starting from wrong assumptions about the root cause.

I would highly appreciate any feedback or tip to continue troubleshooting this issue, if anyone could take a look into the data attached to this post and provide some lights to what to look at, which parameter is out of range, what part could be affected, I would highly appreciate it.

Thanks!
 

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#3 ·
Hei, thanks for your feedback!

I forgot to mention about this, but I checked on my rear brake light, and both lamps, and all of the 3 turn on when I push the brake pedal...I also check on my brake fluid level and it is at max level.

Please let me know your thoughts, thanks!
 
#10 · (Edited)
Hey Solar, how are you? I was able to take out and inspect the Stop Light Switch Assy:

1. Resistance between pins 1 and 2 is below 1ohm for pedal not pressed, and goes above Mohms when pushed = normal
2. Resistance between pins 3 and 4 is above Mohms for pedal not pressed, and does not go below 1ohm when pushed. Actually it does not go any lower than kohms range = abnormal, according to Repair Manual it should go below 1ohm.
3. With a Test Light connected to the chassis its bulb turns on when put in contact with pin 1, and also for pin 3 of the harness that goes connected to the Stop Light Switch Assy = I think this would discard any blown fuse or harness issue.
4. From Techstream Data List I monitored the Stop Light Switch and Brake Pedal Load Sensing Switch = both turned ON and OFF as I pressed/released the brake pedal...sometimes I noticed that there was a delay between both signals status update, but most of the time they changed simultaneously...don't know if the delay could be a sensor status refresh rate from Techstream, or if there is an actual a delay on the switching status update from the Stop Light Switch Assy itself..
5. I had cleared all DTCs yesterday and have not driven the car since 2 days ago. I ran a Health Check not too long ago and P0504 was detected, so it must have appeared while I was troubleshooting the Stop Light Switch Assy today and yesterday...but there was no Check VSC on the instrument cluster, or C1201...

I cannot conclude 100% if the Stop Light Switch Assy is compromised based on the above, but I am considering getting a new one because of #2 test above result.

Anyway, during this week I will continue monitoring the DTCs every time I drive the car to see if P0504 comes up, and when it does, if the Check VSC or C1201 show up as well.

Please let me know your thoughts.

Thanks!
 
#12 ·
Hey Solar, wanted to share an update:

So the P0504 has shown up today, but no Check VSC no Limp mode no C1201...and this time on Techstream the Stop Light Switch signal remained OFF even when the brake pedal was pressed and the light on, so I will replace it...

While I wait for the Stop Light SW Assy I will continue monitoring my car codes and will share any updates...next I will take a look into my Long Term Fuel Trim, I think it is high for both banks so will figure out how to test the MAF with multimeter and Techstream, hopefully it is not something more serious like the catalytic converter? I attach to this post my last Health Check from Techstream. Any comments on this please let me know.

Thanks!
 

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#13 ·
Hey Solar,

I would like to update the current status of my car issues.

I received today the new Stop Light SW Assy. Before installing it I measure the resistance according to the tshooting documentation and it marked the proper values accordingly:
-Resistance between pin 1-2 un-pressed = 0ohms / pin 1-2 pressed = above 40Mohms
-Resistance between pin 3-4 un-pressed = above 40 Mohms / pin 3-4 pressed = 0ohms

I double checked the previous installed Stop Light SW Assy again and between pin 3 and 4 the resistance never reached below 1ohm, actually it jumped all over between koms range, never below or close to 1 ohm...so this SW was definitively compromised.

I proceeded to install the new SW Assy and cleared all DTCs. Then I did a Zero Point calibration from the TIS ABS/VSC Utility by:
1-Doing a [Reset Memory]
2-Doing a [Test Mode] operation

I also would like to mention that before doing the above my car had some other DTCs, I attach to this post my Health Check and some Freeze Frame Data for P0455 and P0175. During the next couple of days I will be tackling these, will be testing the MAF, and already ordered a Fuel Injector Tester and a Fuel Injection Pump Pressure Tester Gauge.

I really hope that the Limp Mode/Check VSC/C1201 has gotten solved with the Stop Light SW Assy replacement, but still the tshooting guide for P0175 and P1170 mentions that any other DTCs should be solved before following its guidelines. Anyway, I will share whatever shows up during the next couple of days.

Thanks again Solar for your support!
 

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#14 · (Edited)
Hey Solar, everyone, how is it going?

I have some updates about my car issue with C1201 and Limp mode.

3 days back I did a Health Check and no DTCs showed up. So today after braking at a traffic light the Check VSC text showed up in the dashboard and the car went into Limp mode again.

I got home, ran a TIS Health Check I have some EVAP codes P0455 and P0441, and a new P1235 [which I attach the Freeze Frame data].

I would like to mention that on previous experiences when my car got into Limp mode with the Check VSC text on the instrument cluster, P1235 has shown up...also P0455 and P0441 have been around.

I have dig around TIS Repair Manual and found this:
Font Material property Parallel Pattern Number


According to this table the Limp mode is a limit FAIL-SAFE condition that triggers because of P1235, so I will move forward tshooting this code. I am thinking about checking pretty much everything on the TIS tshooting guide for P1235, and also checking on the fuel injection pump pressure, injectors cleaning, MAF voltage measurement, doing a recheck on fuel hoses connections, among others, before replacing right away any parts.

I also think that in this last Health Check the Long FT % is high, I would like to decrease it.

I have cleared all DTCs now, so I want the Limp mode FAIL-SAFE limit condition to be triggered again in order to confirm if P1235 or other DTC activates it.

Please let me know your thoughts.

Thanks again for your support!
 

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