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Discussion Starter · #1 ·
I have a 2007 IS250 2wd that has been running great the last 5 years until a month ago, when my starting issue surfaced. It happened the 1st time one morning when I stepped out to go to work, tried to unlock the car door with my key fob....strangely, the car wouldn't unlock. I had to pop out the key cover and manually open the car door. I thought the battery was bad, but it measured 12.9v. Electronic buttons inside the car were found to be unresponsive (ie. can't open trunk, fuel door, lock/unlock, etc) . Anyways, I stepped on the brake and pushed the start button, the car detects the key, the dashboard lights up and dial moves; however, it doesn't crank. The car acts as if I didn't step on the brake pedal and the Engine Start button was amber, not green.

Then out of ideas, I disconnected the battery cable and waited about 15 minutes. Luckily, when I plugged the battery cables back in, the car re-initiated and the engine started. It ran perfectly fine for a couple weeks, then the same issue happened again. I disconnected and reconnected the battery to reset ECU and the car started up just fine. I operated the car to work everyday for a few weeks until it occurred again this morning. I tried to disconnect the battery and plug it back in; however, this time around it didn't work. To rule out any battery issues, I took the battery out of the car to charge it up fully and I also changed the battery in my key fob.

My troubleshooting:
1. Remote communicates (it could activate panic button), but is UNABLE to physically unlock or lock car, open truck (it does beep), etc. It's possible none of the actuators receive any power.
2. I can verify remote key code is sensed and cleared by security ECU (otherwise, it would report as "key not detected" and won't initiate ignition power).
3. No issues with main or exterior electrical power (dome light, dash lights, headlights, etc. works well).
4. Interior / Cabin electrical buttons / solenoids (lock/unlock, windows, side mirrors, trunk release, seats, radio, clock, etc) have no power and are non-functional.
5. Brake pedal remains stiff; cannot depress fully, no brake light (possibly no power to allow brake solenoid to release?); As a result, push-start button is always amber, not green.
6. I was able to resolve the issue a couple times by disconnecting battery cable to reset ECU and have the engine started, but the 3rd attempt failed; car is now disabled.

I highly suspect something relating to the ECU/immobilization system is limiting the electrical power to the essential components in the cabin (in order to start the car); however, I don't have much troubleshooting experience or equipment to go past my current findings. If you've encountered similar issues before or have more troubleshooting ideas, I would greatly appreciate your advice. Thank you.
 

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Sounds like you have a bad body control module
 

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Discussion Starter · #3 ·
Thanks 12VOLT; that was what I'm afraid of (ECU, PCM, computer issues, etc., which are way above my head)! Fortunately, after troubleshooting the whole day yesterday, I was able to confirm it had nothing to do with the ECU, security or immobilization system, but narrowed down the issue to the Fusible Link Block in the engine bay next to the battery. I checked for power with my multimeter in the fuse box and thought it was weird when I was able to get 12.6v at the bolt next to the fuse bar (when moments earlier it was reading 0v). I immediately jumped into the car and turned on the ignition and the radio turned on, which is a good sign. I depress the brake pedal, the light turned green, pushed the start button and the car started right up.

It appears the fuse link has cracked and making inconsistent contact after years of vibrations (see attached picture). When I touched it with the multimeter probe to measure it, the metal came back in contact and allowed electricity back into the cabin. All I had to do in order to reproduce the problem was to wiggle it a bit so it loses connection. The voltage at the bolt will then read 0v. Now that I was able to diagnose the root cause of the problem, it's time to learn how to replace this fusible link block. Thanks for your response!
 

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Great find!
 

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Discussion Starter · #5 ·
Thank God. I thought I might have needed to tow the car to a Lexus dealer to have them begin troubleshooting. This car is 11 years old and has 120k miles, I just cannot afford to spend a couple thousand $$ on this car. Now an OEM Lexus fusible link block will cost me $100 online. :)
 

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I have the same issue. I disconnected the battery, got it charged, and jumped it with a ford f250. Started right up after the cars been sitting for a few months.
Recently i have left it sitting for a few days and it did it again so i thought it was the battery. I found that the battery is good and the key fob works but the dash doesnt come on and the key is red next to the ignition button. Headlights still work but dash doesnt and car wont start! Please help me!
 

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Thanks 12VOLT; that was what I'm afraid of (ECU, PCM, computer issues, etc., which are way above my head)! Fortunately, after troubleshooting the whole day yesterday, I was able to confirm it had nothing to do with the ECU, security or immobilization system, but narrowed down the issue to the Fusible Link Block in the engine bay next to the battery. I checked for power with my multimeter in the fuse box and thought it was weird when I was able to get 12.6v at the bolt next to the fuse bar (when moments earlier it was reading 0v). I immediately jumped into the car and turned on the ignition and the radio turned on, which is a good sign. I depress the brake pedal, the light turned green, pushed the start button and the car started right up.

It appears the fuse link has cracked and making inconsistent contact after years of vibrations (see attached picture). When I touched it with the multimeter probe to measure it, the metal came back in contact and allowed electricity back into the cabin. All I had to do in order to reproduce the problem was to wiggle it a bit so it loses connection. The voltage at the bolt will then read 0v. Now that I was able to diagnose the root cause of the problem, it's time to learn how to replace this fusible link block. Thanks for your response!
I had the same push start button issue. I did everything that you mention and I still can not get the push start button to turn green. There was no crack on my fuse bar and the bolt measured at 12volt.
I can start the car by bypass the starter relay.
 

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I had the same push start button issue. I did everything that you mention and I still can not get the push start button to turn green. There was no crack on my fuse bar and the bolt measured at 12volt.
I can start the car by bypass the starter relay.
Check your brake pedal switch.
 

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Thank you for the response. I did change the brake pedal switch but it did not work. I found out there is a C1241.
C1241 = maybe bad battery . The battery is 3 months ago. any other suggestions. Thanks
That code can be Battery. But load test it and the alternator. Before you throw money and parts at it.
 

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That code can be Battery. But load test it and the alternator. Before you throw money and parts at it.
load test is good. alternator is good.
ecu fuse is open.(no power)
12 ECU- IG LH10 ACruise control, air conditioning system, power steering, rain sensor, antiglare inside rear view mirror, shift lock system, moon roof, tire inflation pressure warning system, (& VSC (2011-2013))
RR fog
11 RR FOG7.5 A
9TAIL10 ATail lights, license plate lights, parking lights
fuse 9, 11, and 12 are open.. the rest of fuses in all fuse box has power. All fuses are good
Reset ECU with pin 4 and 13 did not work. Push Start Start is still amber light.
 

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I checked all fuses and relays only the ecu fuse is open (no power). there is no ecu relay to check.
Is there a way to check ECU??? I had reset the ECU but it did not work.
 

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I checked all fuses and relays only the ecu fuse is open (no power). there is no ecu relay to check.
Is there a way to check ECU??? I had reset the ECU but it did not work.
The main ECU does not control the ABS. There is a separate module. so maybe the pump.
 

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The main ECU does not control the ABS. There is a separate module. so maybe the pump.
I do not think it is the pump. Because i can start the car by bypassing the starter relay. Once I did that check engine will come up. Is it safe on the engine to drive.
 

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I found out today push start button ETA on July 2,2021. I was wondering if you know how to bypass the button, which pin to turn button to green. I am looking for wiring diagram of push start button. Prius use exact button. thanks
 
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