Reading ECU Trouble Codes - Code Breakers

Reading ECU trouble codes can cut trouble-shooting time in half. Just like in the block-buster hit "U-571," when Matthew and the rest of his daring American crew had to steal the Germans code reading machine named "Enigma." With this, the Americans were able to decipher codes sent out by the enemy to put an end to the secrecy. In the fuel injection world, deciphering electronic code is the first step to eliminate the nasty check engine light. Understanding the code can also pinpoint the precise area of malfunction.

So how can I own my own "Enigma" machine you ask? For most cars, it doesn't require breaking into a car dealer to steal the "Enigma" equivalent, all you need is this issue of Import Tuner. As a fair warning, this is only the first step in troubleshooting your car, but it is the biggest step to problem-solving the needs of your Toyota, Honda/Acura, Mitsubishi, Nissan or Mazda.

For the above applications, the rule below will apply for most of the manufacturers we will discuss-don't make me repeat myself. Deciphering codes requires reading the light sequences. With the car in the "ON" position, the light can emit a few different types of flashes. If the light starts out with a long extended flash, this means digits of 10. (Example: one long flash would mean 10) If the light blinks rapidly immediately after, these would be considered digits of one (Example: five flashes would represent 5). Putting our two sets of flashes together, we would end up with the number 15. By referring to our chart for Hondas, we would find our problem is in the ignition system.

If there is a pause between flashes, then it's on to the next code. For example, if there is a long pause between our first two numbers then our first code will be code 15 and our second set of numbers would be our next code.

Honda/Acura 88-'91 Honda; '86-'93 AcuraThese models are by far the easiest to read. The ECUs are equipped with a window on the topside of the computer. On the other side of the window is Honda's "Enigma" machine-well, more like an LED (Light-Emitting-Diode). This little LED holds the key to unlocking the codes to understanding why the damned engine light is on. Simply put, the car in the "ON"-position; watch for the flashing sequence on the LED.

'92-'00 Honda; '94-'00 AcuraAn upgrade from the early-model Hondas, this ECU no longer has the access windows with an LED. Replacing the LED is a flashing check engine light. All that is needed to pull trouble codes is a jumper wire. Locate the factory diagnostic plug located next to the ECU for Integras and Civics or by the center console for Preludes and some Acuras. A two-pin connector contains a brown and black wire. Jump the two wires together and put the vehicle in the "ON" position.

ToyotaToyota is pretty standard with reading code. Most of the trouble codes apply to a majority of its line of cars. Locating the diagnostic plug will give access to pulling your trouble codes. This is found in the engine bay of the vehicle. By using a jumper wire, connect pin E1 and T1 or TE1 (Some vehicles will have pin TE1 instead of T1) and put the vehicle in the "ON"-position. Make sure that all accessories are off and the vehicle is in neutral.

One difference of reading Toyota's code is rather than long pulses to represent digits of 10, Toyota uses short pulses to represent the first digit and uses short pulses again to represent the second digit in a two-digit number. If a vehicle has more than one code, there will be a two-second pause between flashes. This signifies that a new code is going to be revealed. If a repeated code comes up, this signifies that the string of code is starting again.

NissanNissan vehicles require accessing the factory ECU. These ECUs can be placed in five different types of diagnostic modes. For checking trouble codes, the ECU needs to be put into Mode II (Self-diagnostic results). The ECU contains a dial (potentiometer) on the side of the case. This can be accessed by unbolting the ECU, making sure the factory wiring harness is still connected. Place the vehicle in the "ON" position and turn the dial fully clockwise with a flat head screwdriver, wait 2 seconds, then turn the dial back fully counter clockwise. At this time, the check engine light should reveal the vehicle's status. Some of the ECUs will also contain a red LED that will also give flash sequences just like the check engine light. If your Nissan has a green and red LED, the sequences will read as green for digits of 10 and red for digits of one.

MazdaJust like Toyotas, most Mazdas require locating the diagnostic plug beneath the hood and jumping the required pins. Reading the code is just like reading a code from a Honda. Before pulling any codes, make sure the vehicle is in the "OFF" position. The vehicle we tested was a '95 RX-7 but most late-model Mazdas require jumping the same pins in the diagnostic plug. Most Mazdas will apply to this sequence but to be certain check your service manual. Our RX-7 required jumping the "TEN" pin and ground (GND) and placing the car in the "ON" position. Codes are signified through the check engine light on the dash and new codes begin within 4 seconds from the last code.

MitsubishiUnlike most of the cars explained in this story, Mitsubishis require more than just a jumper wire and a check engine light. This vehicle requires use of a multi-meter. The meter will act as your jumper wire within the diagnostic plug. The diagnostic plug is located on the right-hand side of the fuse box and the two pins that will need to be jumped with the meter are the number 12 and 1 pins. With the meter on the voltage setting and the car in the "ON" position, the code could be read in short and long bursts of voltage sent across the meter. Long bursts of voltage spikes signify digits of 10 and short spikes represent digits of one. Codes can be read with a digital volt/ohm meter but an analog meter is much easier to read.