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Skyvisions
Skyvisions, ASE Certified Technician
Category: Toyota
Satisfied Customers: 12722
Experience:  Toyota Master Diagnostic
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Toyota Sequioia: My 01 Sequoia has a c1203 fault (ECM COMM

Customer Question

My 01 Sequoia 4x4 SR5 has a c1203 fault (ECM COMM Circuit Malfunction). Is there something that should be checked? It came on when the mechanic was checking why the brake light was on. That is now fixed, but the ABS and two VSC lights are on.

I would like a solution that does not require me to spend a huge amt of money on a new computer.

Submitted: 1 year ago.
Category: Toyota
Expert:  Skyvisions replied 1 year ago.

Thank you for choosing JustAnswer and allowing me to help you resolve your Toyota questions!

Was the check engine light on it one time?

Customer: replied 1 year ago.

Yes. I brought it in because the check engine light was on


 


PO440 Evap Sys Fault
PO441 EVAP SYS Incorrect Purge Flow
PO446 EVAP SYS Vent Control Fault

I was given a new gas cap which is now installed. Both the engine light and brake lights are off now.

Expert:  Skyvisions replied 1 year ago.
The communication code will be set any time the check engine light comes on. The data link between the two computers becomes interrupted when there is a malfunction in the engine control computer or if the brake warning light is illuminated. The code itself is nothing to be worried about unless it won't clear and this is causing the lights for the VSC system to remain on. If this is the case then there is a problem in the communication line between the VSC computer and the engine control computer. This is extremely unlikely though. Remove the negative battery cable to erase all the memories in the on board systems then see if everything functions normally and this 1203 code disappears.
Customer: replied 1 year ago.

I removed the negative battery cable for 10 seconds and then reconnected it and started the car. The ABS light and the two VSC lights are still lit.

Expert:  Skyvisions replied 1 year ago.
IS the C1203 the only code in the VSC computer? Are there any pending P codes in the engine control computer? Have you driven the car yet?
Customer: replied 1 year ago.

I do not have a code reader myself. The piece of paper the mechanic gave said:


 


SEQUOIA 01 4.7L ABS W TRACK
C1203 ECM COMM CIRCUIT MALFUNCTION


 


I drove it home and it runs fine. Its the first time in months that the engine light and brake light are off for which I am thankful. But am not so happy that the ABS light is on (it wasn't before) and the two VSC light remain lit.

Expert:  Skyvisions replied 1 year ago.
I honestly don't believe you have a communications problem with the VSC system and the engine control system. In 2003 there was a problem with the translate ECU which communicates between the to and would set this 1203 code. The repair for this was to replace the translate ECU. If this problem just occurred after it was recently worked on it sounds like there's possibly an engine control malfunction code setting in the pending portion of the engine control computer which will in turn cause the VSC system to come on. If they are 100% certain that there are no engine control malfunction codes then there may be a data link or communications link problem between the two computers. Diagnosis can be very difficult. I would call the repair shop tomorrow and have them reinspect this to find out what's going on.
Customer: replied 1 year ago.

> If this problem just occurred after it was recently worked on it sounds like there's possibly an engine control malfunction code setting in the pending portion of the engine control computer which will in turn cause the VSC system to come on.

1. So if there are pending codes, can these be somehow cleared and the lights should go quiet?

2. If there is no other problem with the VSC system and the ABS light is cleared in 1. will the VSC lights go out as well?

Expert:  Skyvisions replied 1 year ago.

If the code is not an ongoing or current problem malfunction in the engine control computer then yes normally removing the negative battery cable will wipe the memory clean and should cause all of the lights to go out. However if you're dealing with a malfunction that is current or ongoing the first time you turn the key on and the malfunction is detected it sets in the pending portion of the engine control computer. Theoretically the vehicle skid control light should not come on until it is transferred to the current code system. The VSC light always comes on when there is a loss of communication or anything going on in the engine control computer so that the engine control computer can use the VSC system appropriately for safety reasons. Regarding your number two question answer would be yes. If there is a fault in the ABS system it will also cause a communications code 1203 to set in the vehicle skid control computer. 1203 is lodged in the vehicle skid control computer. From 2001 through 2003 the Sequoia had tons of problems with the vehicle skid control and ABS systems. This was everything from bad computers to bad ground wires and the list goes on and on.

Customer: replied 1 year ago.

Anything I should tell the mechanic tomorrow when I bring it back? Maybe clean the throttle control sensor or something like that (read that that fixed the problem on another forum)?

Since it came on as he was poking around trying to quiet the brake/engine lights maybe he dislodged something or whatever. Any ideas on what he might try?

Expert:  Skyvisions replied 1 year ago.
Having them reinspect their work to make sure nothing was left loose is a good place to start. All of the on board computer systems need to be tested and scanned for possible malfunction codes. Cleaning the throttle body is always a good maintenance issue but generally should never cause this code to set. Sometimes you need to take what you read in different forms with a grain of salt. Throttle sensors technically cannot even be cleaned they are probably referring to the throttle body mechanism itself. It's very possible the memory in the VSC system was cleared when they ran their scan tests and there are probably other codes that they did not list. One of the most common ones is the initialization procedure for the sensors gets lost or the zero point calibration sometimes will be undone. Something just does not add up and without all the information from them it is difficult to say for sure what's going on. Let me know what they tell you tomorrow and post back here and I can give you a follow-up or second opinion tomorrow. I am finished for the evening. Have a good night.
Customer: replied 1 year ago.

As it turns out the Front Right ABS sensor needed replacing (it was broken while the mechanic was investigating the brake light problem).

Now all the lights are quiet now. The only odd thing is that the Skid~ light comes on when ever I start from a stand still. The power cuts out and then a second later comes roaring back. It is a bit irritating.

Expert:  Skyvisions replied 1 year ago.
Was there a code for the ABS wheel speed sensor and are there any codes in there for the yaw rate sensor?

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