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Pulling ECU Codes on your 89 - 96 300ZX

Updated on May 5, 2016

Follow the steps below to pull these codes just by using your hands and a few tools. At the bottom of this page there is a table to assist you in troubleshooting and finding the your problems. Some codes do not trigger a check engine light, so its important to know how to pull these codes from your ECU.

1. Look behind the floor carpeting on the right/Pass side of the vehicle . It's only secured by Velcro.

2. Get a socket wrench and remove the four 10mm bolts holding plywood floorboard. Once removed you should be able to see the ECU in the middle of everything.

3. On the right side of the ECU, Is a screw type potentiometer, and in the hole next to it is the LED the flashes error codes.

4. To get started, put your Key in your ignition switch, turn it slightly but do not start the engine. You just want to apply power to everything without turning the starter.

5. On the ECU with a small flat head screwdriver (tweeker) turn the potentiometer clockwise all the way. Then for 2 seconds leave it at that position, after you count off 2 Mississippi’s turn the potentiometer backwards counter clock-wise. This puts the ECU in its Diagnostics Mode.

6. Now, look to the side and in the hole with the LED. The LED will start to blink fast and slow. A long slow flash indicates the first digit. The quick short flashes are the second digit. (For example One long slow flash and two short quick flash indicate that you have a 12 for an error code.) Write down all your codes from the flashing LED and look them up on the code list below. The check engine light will also flash these codes if you prefer to use it instead.

8. When you’re finished, to return back to normal mode follow the same instructions you used to put the system in test mode. With your screwdriver turn the screw potentiometer clock-wise. Wait 2 seconds, then turn the potentiometer fully counter clock-wise.

LED codes for MODE II:

11:--------- crank angle sensor circuit
12*: --------air flow meter circuit
13*:---------engine coolant temp. sensor circuit
14*: ---------vehicle speed sensor circuit
21: -----------ignition signal circuit
26*: ----------boost pressure sensor
31*: ----------ECU
32*: ----------EGR function
33*: -----------exhaust gas sensor circuit (left)
34: ------------detonation sensor circuit
35*: -----------exhaust gas temp. sensor circuit
42: -------------fuel temp. sensor circuit
43*: ------------throttle position sensor circuit
45*:------------ injector leak
51*: -------------injector circuit
53*: -------------exhaust gas sensor circuit (right)
54: --------------signal circuit from A/T control to ECU
55: --------------NO malfunctions in the above

*Will cause the Check Engine light to come on under normal (MODE I) operating conditions.


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