Question

I have a 2001 Toyota 4Runner with code P0171 and C1201 and the engine and VCS light on

Answer 1

C1201 Engine control system malfunction

P0171 Fuel trim lean Bank 1

When the CK ENG LT comes on the ABS/ VSC are disabled, the manufacturer does this due to the vehicle not being at manufacture specifications. When the vehicle goes lean the fuel ratio is out of specifications, vacuum leaks are some of the main causes, false air leaks at the MAF air duct to throttle body, to low fuel pressure, but for a Toyota, check the sparkplug condition, worn sparkplug will also set a lean code condition.

One of the overlook conditions for a lean code condition is the sparkplug.

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Answer 2

P0171 TOYOTA Code - Air/Fuel Mixture System Lean Bank 1
Read more: https://www.autocodes.com/p0171_toyota.html

C1201 TOYOTA Code - Engine Control System Malfunction
Read more: https://www.autocodes.com/c1201_toyota.html