I did a valve job on my '93 4runner with the 3.0 liter V6 engine. When I finished, it wouldn't start. I quickly determined there was no spark. Running through the troubleshooting chart in the factory repair manual showed all components of the ignition system were fine except the ECM (computer) wasn't sending pulses to trigger the ignitor. The check engine light also quit working so I was unable to read any codes from the computer. According to the troubleshooting chart, this meant a bad ECM.

That seemed unlikely to me since I couldn't think of anything I had done during the rebuilt that would have killed the ECM. I checked all electrical connectors and grounds that I had touched during the rebuild and all was in order.

During further troubleshooting, I finally determined that the MAF (airflow sensor) had shorted. That causes the ECM to shut down. When I unplugged the connector on the MAF, I had spark again.

I just wanted to mention this in case someone else encounters a similar problem. It sure would have saved me time if Toyota had included a check for this in the troubleshooting chart.