Main Relay Circuits - Toyota Engine Control Systems Toyota utilizes several different EFI Main Relay circuits depending on application. These circuits can be categorized into four distinct types. 1) Dual contact EFI Main Relay, ignition switch controlled. 2) Single contact EFI Main Relay, ignition switch controlled. 3) Dual EFI Main Relays, ignition switch or main engine relay blown - JustAnswer Feb 09, 2008Could be the main engine relay/Circuit opening relay or the EFI relay-Try swapping relay around and see what happens. Or get an ohmmeter and test the coil and switch side of the relay. Ask Your Own Toyota QuestionHi there and welcome to JA Could be the main engine relay/Circuit opening relay or the EFI relay-Try swapping relay around and see what happens. Or..With all due respect to the other tech it probably is not a relay. They are not energized until the key is turned on, so unless you had the key in..A relay is just like a switch-having that reverse polarity might have burned it up-have you check all the other small squared colored fusible links..If coil windings of relays are introduced to voltage spikes ( positive or with reversed polarity) it will generally not hurt them. It will only try..Some clarification- If the engine is trying to start check the output of the ignition coil by way of the spark plug wires after you check ALL o..Now we are getting somewhere. The ECU needs to be powered up to turn the light on. And the 7.5 amp gauge fuse powers the check engine light. The EC..If the fuses I mentioned are blown which they probably are, you need to replace them and see if the check engine light comes on. The EFI fuse shoul..Did the fuses get the check engine light on and get the car running? RXXXXX XXXXXIt is unlike that relays are bad 23 years of working on toyotas and I have seen allot of jumped backwards car and they did damage the relays. Are y..I am glad you got it running and you saved a bunch of money and you didn't have to switch to Geico, ha ha ha. In the future you can add a bonus it..