Ignition Signal Test - Code 21
- On 300ZX models and on Maxima, check spark plugs, ignition wires, distributor cap and distributor rotor. If okay, check battery voltage at power transistor. Disconnect the harness connector at power transistor. Turn ignition switch to the "ON" position and measure the voltage. Measure terminals No. 1 and 4 on Maxima, and No. 1 and 3 on 300ZX models. If battery voltage is not present, replace or repair harness.
- If voltage was present, check harness between ECU and power transistor. Disconnect ECU 20-pin connector and check for insulation between terminals No. 3, 5 and ground. No resistance should exist. Place a lead wire across terminals No. 3 and 2 of harness connector, and measure resistance between terminals No. 3 and 5 in 20 pin connector. If no resistance is found, repair or replace harness. If resistance was found, check power transistor for continuity. Refer to MAXIMA POWER TRANSISTOR CONTINUITY VALUES table.MAXIMA POWER TRANSISTOR CONTINUITY VALUES
Tester Terminal (+ / -) Continuity 1/2 Yes 1/3 Yes 1/4 Yes 2/1 No 2/3 No 2/4 Yes 3/1 Yes 3/2 Yes 3/4 Yes 4/1 No 4/2 Yes 4/3 No - On 300ZX models, check power transistor continuity. Using an ohmmeter measure current of tester between terminals 1 & 3, 2 & 3 and 2 & 1. Continuity should exist.
- On Maxima and 300ZX models, if no continuity exists, replace power transistor. If continuity exists, check ignition coil for continuity. Resistance between terminals No. 1 and 2 should be one ohm. Resistance between terminals No. 1 and 3 should be 10,000 ohms. If okay, replace ECU. If not okay, replace ignition coil, and begin test again.