Toyota Tundra Discussion Forum banner

1 - 4 of 4 Posts

·
Registered
Joined
·
4 Posts
Discussion Starter #1
Hey guys! I'm hoping someone might be able to point me in the proper direction. I have a 2007 Tundra 5.7 Crewmax that will not engage the starter relay. The starter solenoid doesn't see a signal, so it doesn't turn over. I bench tested the starter relay, and it's fine. I also swapped it with another relay but I have the same issue.

When I meter the starter relay, I can see that I'm not getting any type of activation. The Fuel Pump and other relays do activate and I can hear things run properly with those.

Inside the cabin, I can hear a little "click", not like the starter solenoid clicking, but a faint click from something under the dash. I've tried starting in both Park and Neutral with no luck. The dash does report the proper gear when moving through the gear selectors.

I did jump the starter relay a few times, and the motor definitely turns over when I do that. I then proceeded to fully start it, and it seemed to idle fine. At some point, while transitioning from Neutral into Drive, the motor just died. I now have the following codes. P335, 340, 345, 366, 390 (Crank & Cam Position sensors). I doubt all these sensors went bad, I suspect there is another cause.

What am I missing? Neutral Safety Switch check? Anything else?

Thanks!
 

·
Registered
Joined
·
4 Posts
Discussion Starter #2
Adding more info. Not sure if this is normal behavior or not. With the key in the ON position, the central dash lights go out in both Park & Neutral only. All other gears, the lights stay on. With the key in the ACC position, the central dash lights are on.

I also jumped the starter relay again tonight. The Dash lights remained off while I was in Park with the motor running. As soon as I switch into a gear... engine immediately shuts off. Same codes as shown above. No codes are shown until I jump it though.

Maybe there is something going on with the Neutral Safety Switch here causing this behavior? Something might be shorting out in those two positions? I'm going to pull the connector tomorrow and jump it again. I'll see what happens. If things look normal, I'll pull that sensor and meter it out, etc.
 

·
Registered
Joined
·
4 Posts
Discussion Starter #3
Well, I wound up finding the problem.

I used this link for 2-day access to all the wiring/troubleshooting diagrams: https://techinfo.toyota.com/techInfoPortal/appmanager/t3/ti

Here are some interesting finds:
  • If you pull the start relay, and don't see 11+ volts on pin 1 with the starter engaged then you'll need to proceed further like I did. However, what through me for a loop was the 9.7Volts I was seeing on PIN-1 when in the ON or Start positions. From what I can determine, this is just phantom voltage from the ECM. Once the circuit really completes, this will drop to near zero.
  • Remember, I jumped pins 3&5 together in the Start Relay socket to test the Starter. That worked fine, so I knew my starter, battery and everything between was OK.
  • If your lights are on and you have the the Starter relay out. You will see NO Lights on the Dash in P&N only. If you put the Starter Relay back in... Lights work normally.
  • I pulled the neutral switch position indicator off. Metered according to manual. All good, but some minor issues at far-end of position play. I fiddled with this thing for quite awhile!
  • All the PRND indicators in the dash, back-up lights, etc work fine with the Neutral Position Switch installed. Remove the harness to the indicator and all of the above fail. Seems like the the switch is fine to me.
  • I jumped pins 4&5 on the Neutral Switch Relay harness to bypass the switch. No dice, same problem as before.
  • I metered pin1 from the Starter Relay to the disconnected neutral switch (pin 5). Wiring was good, no shorts to ground, etc.
  • Disconnected Neutral Switch pin4 shows phantom voltage of 11V with Ignition in the ON position. This actually seems normal. But the phantom voltage threw me off track.
  • Tested Ignition Switch, all good.
  • Tested Dioded that is bundled in the passenger footwell. All good. However, no voltage on input when Key set to Start.
My last ditch effort led me to investigate the ECM... Where I found the below.

883496


Temporarily fixed the wires with jumpers and Truck was back to normal! I believe that brown wire feeds the diode, but I'm not 100% sure, ATM.

Take aways...

Don't let the phantom voltage fool you on the Starter Relay and elsewhere. After all was fixed, I remeasured this again and it shows the 9.7v, but once I insert the starter relay (load) in the mix... that measures near 0.

When I initially opened the hood to investigate this mess. I saw a little tree limb and some pine straw near the battery. Looked like something was starting to build a nest. I looked everywhere for eaten wires, but everything looked great! I guess there is some SOY or something in these lines. Definitely looks like whatever ate at this, preferred that White Wrapping around the bundle towards the ECM.

Finally glad I have a fix for this! Just waiting on getting some better connectors in the mail. Hopefully this helps somebody else.
 
1 - 4 of 4 Posts
Top