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Discussion Starter #1
I attempted to start my 1984 300zx project car today. The car will crank, but it will not start. The Self diagnostics return the codes: 13, 23, and 31. The 23 and 31 codes are expected. The 13 is the cylinder head temperature sensor.

Will this cause the ECU to not start the car? I have checked for spark and there was none.

What events will keep the ECU from sending spark?

Is there a way to test that ECU has made this decision?

Thanks
 

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thansen said:
The 23 and 31 codes are expected.
Why? Do you not have the TPS connected? Is there no electrical load such as heater, headlights or heated rear window?

The 13 is the cylinder head temperature sensor.
Might not a showstopper if the engine is cold.

Will this cause the ECU to not start the car?
No necessarily, but you do need a correctly working CHTS for the engine to run correctly.

I have checked for spark and there was none.
There is your problem. Yay.

What events will keep the ECU from sending spark?
The ECU relies on the Crank Angle Sensor ("CAS") within the distributor to know when trigger the Power Transistor ("PT") which triggers the ignition coil.
Is there power to the PT?
Is there power to the coil?

Is there a way to test that ECU has made this decision?
Do the injectors pulse when the engine cranks?
Are the spark plugs wet with fuel?
A cheap noid light connected to an injector harness should be all that is needed to verify injector pulse.
The ECU relies on the CAS to know when to supply a ground pulse to the injectors.
 

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Discussion Starter #3
Thank you, this gives me some things to check. The throttle position sensor is ok. I just needed to actuate the accelerator to clear it.

Check for injection pulse at the injectors. (should be able to check electrically or by checking plugs for gas)
Check for power and ignition signal working back through the coil and power transistor.
If there is no sign of signal from the ECU, check the crank angle sensor.

One additional question. I have the digital dash. Should all lights on the dash go out during cranking? I read in another forum post the computer is voltage sensitive. Would the dash going dark be a sign of this?
I will add a voltage check at the ECU to my list.

Thanks
 

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Discussion Starter #5
I started my car this evening. Two significant fixes.

It had a bad wire from the coil to the distributor (replaced)
Wired in a new cylinder head temp sensor. (this made a big difference)
I have not actually replaced the sensor in the head yet.

Thanks for the help
 

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do a google search there is a pretty good write up on how to do it. check the wires back as far as you can they tend to get fried up there atop the engine. also check or eliminate the oval connector atop the engine. soldered connections don't fail (when properly done).
 
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