RTH: Immobilizer issue with backup master key (1 Viewer)

[98100Crusher]

I lost the primary key I use with the LC. turning house upside down for it but I've had truck in garage for a couple of weeks working on it.

Situation:
1) I have an original master as a spare key in addition to a valet key.
2) I checked that key is a master by inserting it and the flashing security light goes out. The fob opens/closes doors as well.
3) When I use this key I get the 'no-start' but security light is not flashing. I did try the valet key first but then locked/unlocked the truck with the master.

My first thought was that this master is somehow not paired but in order to pair it I have to start the engine per the toyota process.

Any thoughts would be greatly appreciated.

 

[gregnash]

I lost the primary key I use with the LC. turning house upside down for it but I've had truck in garage for a couple of weeks working on it.

Situation:
1) I have an original master as a spare key in addition to a valet key.
2) I checked that key is a master by inserting it and the flashing security light goes out. The fob opens/closes doors as well.
3) When I use this key I get the 'no-start' but security light is not flashing. I did try the valet key first but then locked/unlocked the truck with the master.

My first thought was that this master is somehow not paired but in order to pair it I have to start the engine per the toyota process.

Any thoughts would be greatly appreciated.

What year truck? Depending on the year you may be able to do the pedal dance to get a new key paired but ultimately to get another master you have to have a master present.
Does the valet key start the truck?

 

[98100Crusher]

What year truck? Depending on the year you may be able to do the pedal dance to get a new key paired but ultimately to get another master you have to have a master present.
Does the valet key start the truck?

1998 LC
Valet does not start truck.

 

[gregnash]

Ok so could be one of two things... 98-00 have a notorious ECU issue where the fuse for the EFI/ECU in the engine bay causes issues and the truck won't start. Sounds like you may know of that one already.

Or, neither of your current keys ever had the transponder programmed properly to the system OR the ECU itself has gone bad. Any chance you have access to TechStream? Not sure if a normal OBDII scanner would show a trouble code for an ECU malfunction.

Calling @Mauser

 

[98100Crusher]

Ok so could be one of two things... 98-00 have a notorious ECU issue where the fuse for the EFI/ECU in the engine bay causes issues and the truck won't start. Sounds like you may know of that one already.

Or, neither of your current keys ever had the transponder programmed properly to the system OR the ECU itself has gone bad. Any chance you have access to TechStream? Not sure if a normal OBDII scanner would show a trouble code for an ECU malfunction.

Calling @Mauser

That's the puzzling part, I thought I tested the master when I bought the truck four years ago but its acting like the master is unknown to the ECU which is a very unhappy and expensive scenario.

 

[gregnash]

That's the puzzling part, I thought I tested the master when I bought the truck four years ago but its acting like the master is unknown to the ECU which is a very unhappy and expensive scenario.

If you happen to do through dealership yes... @Mauser has helped another MUD'r with a similar issue that his ECU for the Immobilizer crapped out and luckily he had a spare that he was able to swap with the user as a virginized ECU. IF this becomes the case where you can't find the key you had, and you can't get a locksmith to be able to program new ones to start the truck AND have determined it IS NOT the EFI relay issue, then a virginized ECU will be the way to go.

 

[Mauser]

If the security light is going out when the key is inserted into the ignition then the key is recognized by the ecu and that isn't the issue.

It could be another issue with the ecu, but I really haven't run across too many failures.

I would start by checking grounds, and the crank sensor and its wires.

I do have an ecu for your truck, if you get to the point that you are ready to try replacing yours let me know.

 

[98100Crusher]

If the security light is going out when the key is inserted into the ignition then the key is recognized by the ecu and that isn't the issue.

It could be another issue with the ecu, but I really haven't run across too many failures.

I would start by checking grounds, and the crank sensor and its wires.

I do have an ecu for your truck, if you get to the point that you are ready to try replacing yours let me know.

Would ECU recognize generic, never-associated master as a master? I've never had an issue with starting the car with the lost key. My assumption at the moment is that I did not check that this master worked when I got the vehicle and the seller (dealer in TX) threw the keys in with the sale without pairing them to ECU.

 

[Mauser]

Would ECU recognize generic, never-associated master as a master? I've never had an issue with starting the car with the lost key. My assumption at the moment is that I did not check that this master worked when I got the vehicle and the seller (dealer in TX) threw the keys in with the sale without pairing them to ECU.

No, if it was never paired then it wouldn't recognize it. If the security light does quit flashing when you insert the key into the ignition it is being recognized.

I am happy to send you an ecu if you want to try one. If it fixes your problem we can work something out.

 

[98100Crusher]

No, if it was never paired then it wouldn't recognize it. If the security light does quit flashing when you insert the key into the ignition it is being recognized.

I am happy to send you an ecu if you want to try one. If it fixes your problem we can work something out.

Update:
Yes the backup key was a master key. My problem was a mildly flat battery! It would light up normally but didn't quite have enough juice for normal start up. I put the battery on the charger for 14 hours and voila started with both backup keys.

Thank you very much for the expert commentary. Based on the information provided I took a step back to do a mental debug 101 of what changed besides the key - in this case it was that the truck had been sitting in the garage and hadn't been turned over for three weeks.

The good news is that I now know a lot more about my keys and the ECU (I was reading the articles on DIY flashing to understand what goes on). You never understand something until you have to build it or fix it.

Time to get another master key and do the pedal dance.