2007 Sequoia stopped while driving- no crank

Hi everyone, I have a 2007 Sequoia SR5 with 117K miles on it. Timing belt/WP changed recently. Truck shut down today while driving on the interstate. Had it towed home, nothing happens when turning the key to start position. I suspect an electrical issue. All the electrical accessories work fine. I have no communication with the OBD port with a scan tool or with Techstream. No CEL on the dash.

In attempting to diagnose it, I disconnected some of the connectors from the ECU. When I disconnect the furthest left connector (E8 on the wiring diagram) I get communication to the OBD port and the truck will crank but not start. As soon as I reconnect that connector, communication is lost again and no crank. All fuses look good.

Has anyone ever had issues like this before? It seems unlikely to be an ECU issue, as I can read codes and communicate with it as long as that one connector is disconnected.

Thanks in advance.

 

Follow and check that ground as it's shorting out the harness.

 

Which ground are you referring to? Thanks!

 

ECU, Engine grounds. There may be a damaged wire on that harness and an additional ground looped in there. Finding it is the issue. Maybe off a module.

 

You may need to pull up the wiring diagram and follow that harness down to where they go.

 

I did pull up the wiring diagram, and I located the connector. But then on the diagram of the ECU I couldn’t seem to find the connector. I’ll have to give it some more time.

 

Check out this post, possible the wire got cut by the belt after water pump? This normally throws a check engine light tho. Happen to me

https://www.tundras.com/threads/p0335-after-timing-belt-replacement.139152/

https://www.tundras.com/threads/p1340-igniter-circuit-malfunction.53386/

 

Good thoughts. I checked the wires from the crank and cam sensors and traced them back to the main harness. They looked good. Didn’t see any place where they were shorted to ground visually.

 

I would take a closer look at the camshaft position sensor not necessarily visually but with a VOM(volt ohm meter) if you have one, in particular a short to ground of the Grn/Blk conductor.

With your ECU E8 connector and your Camshaft position sensor unplugged, if the Grn/Blk pin 23 of ECU E8 connector shows a short to gnd, that's not good.

The ECU E8 pin 23 is the VC (voltage control) signal they are speaking of in below TIS Technical Training article.

It's somewhat plausible given you unplug E8 and OBD works and you mentioned no CEL.

 

I'm gonna dig into this in the morning. I messed with it a while today and wasn’t able to find any visually identifiable damage to the CPS. There is only one on this vehicle that I can find- under the plastic timing belt cover on the driver’s side. The passenger side cam doesn’t seem to have one. Is that correct? I’ll hit it with a multimeter tomorrow and check for shorts to ground.

I tried several time to get communication from the ECM with the cam and crank sensors disconnected, but no results.

 

If it's indeed the conductor I mentioned(Grn/Blk), having either sensor unplugged will not help validate, especially if the ECU E8 connector was plugged in.

 

Thank you. I’ll check for a short to ground on the green/black conductor.

 

Yes, there is a short to ground on E8 pin 23, black/green, with the camshaft position sensor unplugged. I guess I need to track that down? That should not be present I assume. What other sensors are in that voltage control circuit?

 

The wiring diagram indicates that it should be a straight run from the camshaft position sensor to E8. I will investigate this.

 

I replaced the green and black wire. Now the engine will start and run but there is almost no response from the throttle pedal.

 

Which wiring diagram are you using ?
The 2007 Sequoia EWD that's available here in the Electrical Forum clearly shows the path from Camshaft Position sensor starting at page 91 Engine Control as it heads to ECU E8 and other circuits.

I'm not positive your ground check is valid if you did not undo the other components junctioned with that conductor.

If you look at that picture I posted above, that Grn/Blk wire leaving E8 pin 23(+5vdc Voltage Control) comes to a junction and also goes to the Throttle Control Motor and Position Sensor also as a +5vdc Voltage Control, which I highlighted in above pic. That's probably the reason for your Throttle issue and codes if you inadvertently removed/bypassed that circuit.

If you replaced straight from Camshaft Position to the the ECU E8 pin 23, you did away with a number of junctions feeding vital items.

 

Same diagram as you posted. But I clearly missed that there is a junction in that wire feeding other sensors. Back to the drawing board.

 

Found it. Melted wire near the muffler behind a frame brace underneath the truck. Harness controlling evap canister and fuel pump.

 

Great work....that was part of the circuits where I mentioned "feeding vital items" that you hopefully saw when following the wiring diagrams.

 

Yep! And it was because of your help that I started tracing the wires toward the canister. Thanks again. Probably saved myself (my dad actually, it’s his truck) a $1500 shop bill.

 

Your Welcome....you did the rooting around under truck while I crashed on couch watching U.S Open on Fathers Day