Cold Air Intake = Check Engine Codes


My 2001 Toyota Celica GT-S has had an Injen brand cold air intake installed for a few years.

The engine short block was recently replaced by Toyota with a new one (after water had been sucked up into the motor) along with the mass air flow sensor and the fuel injectors. I had the car for only about a week or two before the check engine light came on again. It had also been on before the engine was replaced.

I?ve had it to two Toyota dealerships who have said the codes indicate anything from a catalytic converter fouling to some vacuum leak somewhere. Neither dealership was able to come up with what was exactly causing the CEL much less a solution.

Looking on some Celica user groups as well as talking to some local tuners, a common thought is that the cai is causing the code and that there is basically nothing I can do about it.

I was hoping for your thoughts. I’m now selling the car. The engine codes are P0440, P0441, P0420, P0446



One of the codes could point to either a failed post-cat O2 sensor (possibly damaged by the water) or a faulty converter.
The other codes refer to the evaporative emission system (gas cap, canister, purge solenoid, vacuum lines, etc.)

It will take further diagnosis to determine exactly what the problem is but I don’t see the CAI as being the culprit at this point.
I have no idea why they can’t seem to figure this out; it really should not be difficult at all.

This is more of an emissions problem rather than one that will cause the car to quit or run badly.


An independent shop might be more willing and more capable. Ask around.


It seems to me that there is a problem in the evap system, and this is pointing to a vaccum problem somewhere. Put a vacuum gauge on a manifold source, and check for vacuum around 20-23 in Mg. Then, pull the vacuum line running the the charcoal canister, and check the vacuum there. This sound like a failed vacuum switch or a collapsed or plugged line. I’m leaning to a failed vacuum switch or a bad purge valve with the malfunction code and weak purge flow. There is also a thermo vacuum switch on the intake near the thermostat that could be bad, and not opening up the purge circuit once the car is warm. This should not be hard to figure out. I don’t think the CAI has a thing to do with it, and the dealer mechanics are just being lazy.

Code results:

P0420 Catalyst System Efficiency Below Threshold (Bank 1)

P0440 Evaporative Emission Control System Malfunction

P0441 Evaporative Emission Control System Incorrect Purge Flow

P0446 Evaporative Emission Control System Vent Control Circuit Malfunction


Can you tell us how the water came to be ingested? That may provide a clue as to why you have the EVAP copes. I’m wondering if the charcoal canister and purge valve were immersed.

I just realized that if the engine died while the exhaust system were submerged and water flowed back into the system, that could be a clue to your cat code too. Just a wild thought.


I had the same three evap codes, somewhat intermittently, and it was the charcoal canister assembly on my 2002 Sienna. There are allegedly some low pressure valves there that stick. I had someone replace it, but you can save money, and some say it is not hard to replace. If the canister has never been replaced, I’d bet on it, but of course it’s your money, not mine.

On the other hand, a gas cap can also cause those evap failures. So, try a genuine $20 Toyota gas cap, reset the codes, and run a few days before trying canister, Brand-X gas cap simply does not work reliably, I tried it.

This problem looks like two separate issues, evap is not related to other code at all, and there is no reason to think CAI has anything to do with it.


Let me explain those evap codes. The computer, under very precise operating conditions, shuts off venting of fuel tank, then measures the tank pressure for a certain length of time, and it should hold pressure within specs. If it loses pressure too fast, it gives you those codes. Thus, bad gas cap which vents too fast can do it. Also, those valves (not VSV’s) on canister can also cause it.

This is a time to read the Sienna Club, though you might not want to join up since you don’t have a Sienna. :slight_smile: