2004 Toyota Camry, Engine Speed Will Not Accelerate Past Idle

This 2004 Toyota Camry was towed in with the complaint that the engine would run but it would only idle. The alternator had failed and after the alternator was replaced the condition developed. The “Check Engine” light was on so I checked codes. P0113, “Intake Air Temperature Circuit High Input” and P2118 “Throttle Actuator Control Motor Current Range/Performance” were stored.

I read up on the P2118 code information and found that it directly relates to the lack of current available and that it specifically relates to power from the ETCS fuse in the underhood fuse box. I identified the fuse in the fuse box legend that is located on the inside of the fuse box cover.

After locating the fuse I tested it with a test light.

Power on one side of the fuse and none on the other of course indicates a blown fuse.

If you look closely at the fuse in the next picture you should be able to see the top of the loop missing. You may need to click on it to enlarge. I replaced the blown fuse. Feeling pretty good for the customer, I started the engine only to find the problem had not been resolved.

I checked for more blown fuses and found one in the under dash fuse box marked RAD2 that was blown. Replaced it and still had the same problem. On an educated guess I cleared the code with my scan tool and rechecked the engine performance. It was now operating properly. If you do not have a scan tool to clear the codes, simply disconnect the battery for about one minute.

After the fuse had been replaced and the codes were cleared the check engine light was out. I took the car for a test drive and all was well.

Now you may ask, “Why did the fuse blow in the first place?”. The answer is basic math. There is a formula for this but simply put, we have a 10 amp fuse protecting a 12 volt electric motor. We can surmise that there is a amperage buffer built into the fuse rating. The throttle body motor should draw between 6 and 8 amps on a normal basis at a nominal 12 volts. If the supplied voltage drops to half of the design voltage the amps drawn will about double. So we know that the alternator failed and I found out that the engine stopped running from low voltage. For the sake of simplicity let’s assume that the system voltage was between 6 and 7 volts when the engine died. The current drawn from the throttle body motor would have been between 12 and 16 amps. Thus causing the fuse to blow.

Something else worth noting is that the design engineer installed a failsafe in the system so that if there is not adequate current available for the throttle body motor to function properly, a code P2118 will set, the code will have to be knowingly removed in order for the system to operate properly again.