2000 Avalon - Cranks, no spark, no start, no codes.

I can create codes by disconnecting MAF (for example) and I can clear them with my cheap scanner. The CHECK ENGINE light does NOT come on with the key on....this is supposed to be an indication of a bad PCM but then why can I create codes?

At one point I got a code that indicated a TPS and I replaced that. I have checked all fuses but wrecked the main relay trying to get it out. I do get a 5V signal on the TPS pin 1, but the other pins do not show the proper voltage.

Where can I find pinout diagrams for the PCM? Do any of the less expensive scanners include this kind of diagram? I found a wiring manual on Ebay but have no idea if it would include the PCM diagram I need.

Hardrock wrote:

I can create codes by disconnecting MAF (for example) and I can clear them with my cheap scanner. The CHECK ENGINE light does NOT come on with the key on....this is supposed to be an indication of a bad PCM but then why can I create codes?

How many miles on this Avalon? It might be that the MIL just doesn't work anymore. :silly: For me, if you can communicate and create codes, then I'm not counting the inop MIL as a red flag.

At one point I got a code that indicated a TPS and I replaced that... I do get a 5V signal on the TPS pin 1, but the other pins do not show the proper voltage.

Were your readings at the TPS taken with the sensor plugged in, or backprobed? What were your readings, exactly?

Where can I find pinout diagrams for the PCM? Do any of the less expensive scanners include this kind of diagram? I found a wiring manual on Ebay but have no idea if it would include the PCM diagram I need.

When you say pinout diagram, do you mean a voltage reference chart for each pin on the PCM? Or do you mean an engine performance wiring diagram like Paul uses?

Either way, I'd try something like MitchellDIY or Haynes. They're both available online for a reasonable price. Haynes also has a printed version available depending on your preference:

haynes.com/en-us/toyota/avalon/1997-2001-1

www.eautorepair.net/marketing/default.asp

I have checked all fuses but wrecked the main relay trying to get it out.

Yeah, those relays really don't want to come out. :silly: I'd say replace that relay with a new one and continue your testing.

Do any of the less expensive scanners include this kind of diagram?

Not likely, no. Even if a scanner offers wiring diagram access, it's usually on a yearly subscription service.

200K milage

TPS reading was NOT plugged in....my book said to do it this way. Pins 2 and 3 showed Voltages barely above zero. Pin 2 should have been between .03 and 1v (if memory serves). I believe the 5V on pin1 was supposed to indicate a connection to the PCM; power that is.

The diagram I want would show the PCM and which wire is getting power from the battery and what all the other wires are connected to....TPS, MAF, CPS, Cam sensor, etc.

I keep wondering if the timing belt is the issue since I believe that it's failure would NOT throw an error but would cause the no spark.

you said: The PCM provides power and ground to the sensor. 5V Reference on pin 1, pin 2, throttle fully closed 0.3-1.0V and fully open, 2.7-5.2V. Pin 3, ground. Does pin 2 go to 5V when you unplug the sensor? If it doesn't, Can you ohm the signal wire( Pin 2) to ground, meter on the highest scale with both sensor and PCM disconnected?

I'm using a Haynes book and the Voltages shown there match what you have provided above. I followed instructions in the book and tested pin one DISCONNECTED. Then reconnected TPS sensor and backprobed pins 2 and 3. The Voltages were way low. Replaced TPS..... I'm not sure if I backprobed the new TPS to see if that corrected the voltages. I will try that.,,,,and I will try your other suggestions above.

When you say check resistance on the signal wire with PCM disconnected, do you mean disconnect all PCM connectors/wires? How do I find out which connector is for the TPS? That's why I was trying to find a diagram. THANKS!!!

It was a transponder problem.....

:silly:

Well hey, it's fixed! We genuinely appreciate the follow up with what you found.

For our reference, was the key/immobilizer light going off before you found the duct tape issue? Did the MIL come back to life after the fix?

The security light was flashing and should have gone OFF when I inserted the key. Since it did not, I remembered the previous problem with the transponder.

I wonder how many of the crank/no start problems people describe are due to a simple transponder failure. The good news....this detective work has rekindled my interest in troubleshooting. When you're retired and have the time, it's kinda fun. When you've got to get to work, you just want it fixed.

The check engine light did not come on after this was resolved....I can only assume that the bulb is out.