No Crank/No Start/No ECU communication 07' 100

[alecrexmac]

Hey everyone,

I’m having some strange issues with my ’07 100 and could use some insight.

Here’s the background:

I’ve been working on fixing it up and recently took it camping. It was running fine—got to the campsite, parked it for a few days. When I went to start it back up, I turned the key to the run position, it did nothing for a second, then cranked and started. I noticed this but brushed it off as user error. I drove it around with no problems that day.

The next day, though, I tried to start it, and now there’s no crank. My first thought was that it might be the battery, so I checked all connections, tried a jump pack, used jumper cables, and even swapped the battery from a GX. Still nothing. Thankfully, my brother came to the rescue and flat-towed us home.

Here are the symptoms:

• All interior electronics and external lights are working, and the key unlock works fine.
• Tried the spare key—no difference.
• Jumped the starter relay, and the engine cranks, so the starter seems to be working.
• I can hear the relays clicking when I turn the key to the run position.
• No communication with the ECU using either a Bluetooth scanner or a regular scanner (going to try my Techstream laptop today, but I don’t expect a difference).

My current thinking:

• From what I’ve read, immobilizer issues usually lead to a crank/no start situation, so I’m leaning away from it being an immobilizer issue.
• Could it be a fuse problem?
• Why is the ECU not communicating? Could it have failed?

Next steps:

• Find the relevant pinouts and check for ECU power and fuses.
• Possibly replace relays.
• Explore ECU replacement options.
• Hope to get some advice here on what to try next.

Any thoughts would be really appreciated! I’ll keep this thread updated as I work through it.

 

[alecrexmac]

Small update,:

• Continuity tested all fuses, no issues.
• Verified OBD2 function using tech stream. Communication was established with all systems except ECU. Immobilizer showed no codes. Uploaded a picture of it.
• Checked voltages on all fuses. I noticed that all fuses read 12.03V except one on the right hand side kick panel fuse box. It was the one of the ECU fuses, reading 11.93V. I am not sure if this is significant but it was different from all the others.

 

[excessive]

check all the grounding cables for corrosion. Also check your battery connections for tightness/ corrosion

 

[alecrexmac]

check all the grounding cables for corrosion. Also check your battery connections for tightness/ corrosion

check all the grounding cables for corrosion. Also check your battery connections for tightness/ corrosion

No corrosion, connections are tight.

I also checked:

• EFI relay circuit into engine ECU.
• EFI relay working.
• Starter relay working.
• ECU is passing IGSW to MREL energizing the efi relay.
• Backprobed the ECU it has B+ and ignition switched voltage.

Still no communication with the ECU, would anyone know how to verify that it is functioning?

I could still check the ignition switch but it doesn't seem like the culprit.

 

[Trunk Monkey]

What's the immobilizer security light doing when you put the key in?

 

[alecrexmac]

I have an aftermarket radio so I do not have the light. I checked in tech stream and I didn't show any issues with the immobilizer. Also, I get no crank at all and from what I have read immobilizers issues will crank but no start.

 

[alecrexmac]

Backprobed the ECU further to verify:

• ECU is gets voltage from battery E11-3
• E11-1/2 have voltage when key is on
• IGSW E11-9 has voltage when key is on
• MREL E11-8 has voltage when key is on

Jumped the EFI relay to see if any change, nothing.

Visually inspected ECU board for damage or water, nothing to note.

I have ordered new EFI/starter relays, fuses, and a ECU from ebay. It wasnt cheap, but I have verified voltage is where it needs to be and nothing is responding.

If anyone has any input let me know. The current troubleshooting has ruled out relays, fuses, grounds, ignition switch, starter, battery, imobilizer. I am guessing the ECU fried.

Backprobed the ECU further to verify:

• ECU is gets voltage from battery E11-3
• E11-1/2 have voltage when key is on
• IGSW E11-9 has voltage when key is on
• MREL E11-8 has voltage when key is on

Jumped the EFI relay to see if any change, nothing.

Visually inspected ECU board for damage or water, nothing to note.

I have ordered new EFI/starter relays, fuses, and a ECU from ebay. It wasnt cheap, but I have verified voltage is where it needs to be and nothing is responding.

If anyone has any input let me know. The current troubleshooting has ruled out relays, fuses, grounds, ignition switch, starter, battery, imobilizer. I am guessing the ECU fried.

 

[Trunk Monkey]

Highly unlikely for an ECU to just go bad, can't think of a single report of it here.

 

[alecrexmac]

Highly unlikely for an ECU to just go bad, can't think of a single report of it here.

Yes that is what I have been seeing as well. I am still working on it. I did notice that the coil side of the starter relay has a constant 8 V on it which is strange but no response from the key being turned to ignition. I am weeding through the wiring diagram currently.

 

[alecrexmac]

Hi anyone who may come across this thread. The culprit ended up being a shorted 5V reference signal on the VC circuit. It was the wiring for the camshaft position sensor, but interestingly the internal wiring and not the wire bundle that runs across the timing belt.

For anyone trouble shooting a similar issue, backstab the VC pin on the ECU and see if the signal deviates from the 5V. If so, you will have the no communication, no crank, no start and you will be very confused. Another option is to unplug all the components on the circuit and see if the condition changes. I have attached the wiring diagram from my particular LC. Hopefully this helps anyone in the future.

Thanks.

 

[BenScott]

So replacing the camshaft position sensor resolved the issue? I experienced a similar no start issue that you described.

 

[alecrexmac]

So replacing the camshaft position sensor resolved the issue? I experienced a similar no start issue that you described.

Yes, replacing the sensor resolved all issues. If you are having issues similar to mine, a good place to start is just unplugging the sensor and checking if ECU communication is restored or a crank is restored. It will not start unplugged. It can be any of the components on that 5V circuit so go systematically until a culprit if found. Good luck.

 

[BenScott]

Yes, replacing the sensor resolved all issues. If you are having issues similar to mine, a good place to start is just unplugging the sensor and checking if ECU communication is restored or a crank is restored. It will not start unplugged. It can be any of the components on that 5V circuit so go systematically until a culprit if found. Good luck.

I think my issue was with the starter relay. I pulled out and reinserted the current one and haven't experienced the issue again but I did pick up a replacement just in case.

 

[alecrexmac]

I think my issue was with the starter relay. I pulled out and reinserted the current one and haven't experienced the issue again but I did pick up a replacement just in case.

Nice glad to hear it was a easy fix.