NA6 ECU Problems
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I recently bought a 93 miata with a blown motor, and swapped a good motor into it. The ECU, dash, and engine are all from a 90. The car is electronically stock.
From what I understand, there are no compatibility issues with any dash, ecu, motor, and chassis configuration from any combination of different NA6's.
At the main power for the ECU (red/blue wire) I get 12.5v, and at the main 12v power output of the ECU (red and white right next to the other wire) I get only 1.3v. At the solid purple wire (also a 12v power output i think) I get only 9v.
Does anybody know what on earth could be wrong here? I have already swapped to a tested ECU and all voltages tested exactly the same.
From what I understand, there are no compatibility issues with any dash, ecu, motor, and chassis configuration from any combination of different NA6's.
At the main power for the ECU (red/blue wire) I get 12.5v, and at the main 12v power output of the ECU (red and white right next to the other wire) I get only 1.3v. At the solid purple wire (also a 12v power output i think) I get only 9v.
Does anybody know what on earth could be wrong here? I have already swapped to a tested ECU and all voltages tested exactly the same.
Last edited by demosthenes384322; 02-06-2019 at 05:16 PM. Reason: spacing
#14
Tweaking Enginerd
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You need to be methodical here. Replacing parts and testing partial functionality isn't the best troubleshooting method.
Get the schematic.
Confirm or deny that you have 12V on the WHT-RED ECU pin 1B KOEO
If you don't...
Trace forward from the battery or backward from the ECU to find where the fault is.
Power sequence is
Battery
INJ fuse
Main relay
Battery
MAIN fuse
IGN switch (KOEO)
ENGINE fuse
Main relay
Main relay
ECU pin 1B
You need both the INJ fuse path and the IGN switch path for the main relay to work. Confirm the functionality of each element in-circuit.
Get the schematic.
Confirm or deny that you have 12V on the WHT-RED ECU pin 1B KOEO
If you don't...
Trace forward from the battery or backward from the ECU to find where the fault is.
Power sequence is
Battery
INJ fuse
Main relay
Battery
MAIN fuse
IGN switch (KOEO)
ENGINE fuse
Main relay
Main relay
ECU pin 1B
You need both the INJ fuse path and the IGN switch path for the main relay to work. Confirm the functionality of each element in-circuit.
#16
Cpt. Slow
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If power to the relay tested good, then the relay is either not being triggered, it's bad, or there's a short in the wire between the relay and the ECU. Your ECU is fine, it's just not being powered on.
Relays have 3 inputs, and one output. Two of the inputs are smaller pins for the coil. One will be 12v, the other ground. If both of these are present, the relay will complete the circuit by connecting the third input (12v) to the output pin. So test all of these with the batter on, and tell us which one you don't have. To test that output, put your multimeter on resistance and check from the ECU's R/W wire to the R/W output pin of the relay, you should read less than an ohm.
Relays have 3 inputs, and one output. Two of the inputs are smaller pins for the coil. One will be 12v, the other ground. If both of these are present, the relay will complete the circuit by connecting the third input (12v) to the output pin. So test all of these with the batter on, and tell us which one you don't have. To test that output, put your multimeter on resistance and check from the ECU's R/W wire to the R/W output pin of the relay, you should read less than an ohm.
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