1988 V6 5-speed, Check Engine Light comes on after driving for a while. It can take up to 10-15 minutes to register. If I park it, then return later, it stays clear for a while, then it turns back on.
I performed the EFI diagnosis:Engine normal operating temperature, all accessories off, shorted T & E1. The check engine light is supposed to blink once every 0.25 seconds upon Normal System Operation. Or, it is supposed to blink accordingly to the codes.
Here's what it does: After turning the key to the On position, the check engine light will turn on (steady), then I short T & E1 and the check engine light remains steady, almost like I didn't even short it. I even tried to short it with stranded wire. I've done this before, with no problems. It doesn't even blink Normal.
The book also states, "All detected diagnostic codes, except 51 and 53, will be retained in memory by the ECU from the time of detection until cancelled out." Code 51 is Switch Signal- Air conditioner switch ON, neutral start switch OFF, Idle switch OFF during diagnosis check. Code 53 is Knock Control Signal in ECU- Knock control program fualty.
Furthermore, the flowchart states, "Does the CHECK ENG. light come on when ignition switch is at ON?---------->Yes--------->Normal." Also, " Does the CHECK ENG. light go OFF when engine is stared?-------->Yes------->Normal. Like I said earlier, the check engine light come on after driving for a while.

Can you get a spare ECM from a salvage yard to test yours by replacement?

Wouldn't that be an expensive test?

Only way of testing your ECM I can think of without actually buying one new.

I don't know the cost. The other option is bringing it to Toyota and paying them for their opinion.