(WARNING: WALL OF TEXT)

Hello, literally made this account as a last ditch effort as I haven't seen anyone else experience this via forums (through my hours of Google search and days in my friend's garage...lol),

2008 Lexus IS250 (MT) -- High mileage ( 390,xxx km on body ) with known motor swap (No oil loss and motor runs amazing along with great shifting transmission - thankfully...)

Car is running Catless (Rich) no tune yet to compensate; so CEL is normal and I scan the codes periodically to ensure things are good. (9.5 - 11.2L/100km fuel mileage for the curious)
Catless headers and 3" single exit exhaust,

Besides that; VSC light and TPMS is on (TPMS due to no sensors and VSC is unknown)

Car running fine driving, shifts great, runs as it's supposed to.

PROBLEMS/ISSUES:

- Parking Brake Light on
- ABS Light on
- Passenger Airbag Light on
- Power Steering Light on (Loss of power steering)
- Ambient Temperature sensor not working
- Climate Control wouldn't work / respond (Found out it was low coolant possibly - topped up - heat works now, and hasn't stopped responding...yet...)

- OBDII won't communicate to ECM (!!!)
tried a $5000+ reader that can work its magic, and tried a Bluetooth (BlueDriver) to connect -- nothing can pick up or read any codes any longer. (As I was able to periodically)



Traced these symptoms to Fuse 18 in Driver footwell fusebox (Fuse 12: ECU IG-LH) that runs all of these systems and more;
so I checked the 10A fuse and it was blown - replaced it.

All lights come back on 2-3 weeks later and I check the fuse again - 10A fuse is blown again; replaced.

Lights come back on after 30 minutes of driving the same day, and I check the fuse...10A fuse is NOT blown.

I start to panick as I replace the fuse anyways but the lights aren't leaving.

I can still drive the car, shift properly, no bogging, rough idling, etc.

I bring it to my friend's garage to diagnose with our grubby hands in the Canadian cold and pull out the ECM:

No corrosion, no moisture, nothing. The ECM is perfectly preserved in its sarcophagus.

Pull out PCM under the Car's battery:

Nothing out of the ordinary, some moisture as the battery isn't 110% moisture proof and have water run down the side of the engine bay wall.

I go to my BlueDriver's Saved History Reports and have P0606 for PCM/ECM Processor failure - yet it can definitely be a false negative from my Downstream o2 sensors reading incorrectly and throwing off the ECM itself;

but all these codes and errors coming up --- going from a perfectly working Power Steering function, functioning OBD2 port, Climate Control working, Airbag light off, ABS light off, etc...

to all of it going wrong at once;

Anyone else have any clue?




I'm seeing IS250 ECU send and repair services for $100+ USD but trying to contact some people locally to see if they can do it and faster...

Other than that, no loose ground wires we could see thoroughly, no exposed wires, nothing major, no corrosion, etc.




Current update:

Drove it home, letting it relax in my driveway; car's climate control works as normal and responds after coolant top up

I can still drive perfectly fine, just no ABS, Power steering and having a airbag light on.

My friend and I narrowed it down to ECM after checking other fuses, as my power windows work, headlights work, turn signals all work, radio works, sound works, etc.

No engine problems, transmission shifts fine, engine is good and accelerates smoothly...

Anything else before I attempt to send off my ECM for repair?

Thank you

 

If that fuse keeps blowing, I bet there's a short somewhere in the line. Did you get a TIS subscription to see the diagram?

 

The fuse stopped blowing after the second time; I've checked and its been fine.

But all the lights on the dash are still lit.

Buddy and I tried communicating to the gauge cluster (works) but anything to the ECU - no signal/communication.

 

I don't know who needs to hear this, but removing the cats is like removing a gallbladder, then being surprised by side effects...

 

I've always ran catless exhaust systems with no problems or issues in a multitude of my vehicles...

I understand your perspective - and I know a CEL and some P0XXX codes are to be expected along with poor gas mileage and A/F Ratio numbers being off depending on how the o2 Sensors are integrated into the new exhaust system. (Running on Factory tune and no aftermarket tunes to compensate for the new system)

Thank you for your input though; any input in regards to the ECM and communication itself? Or know of anyone with similar experiences?

Thank you.

 

Check your radiator housing to your ECM Plastic box, for a tube that channels hot air onto the ECU. If you have one of those, the hot air and cold ECU/box creates condensation. Where electronics love to live in, moisture.

 

Checked for any passageways, along with corroded wires and moisture - nothing. None of the wires or connectors look like they've seen moisture or any outside exposure that could damage them. (Thankfully they're in the screwed down and enclosed box lol)

ECM is enclosed as well and it's bone-dry besides some dust. Only moisture we've seen was underneath the car battery where the PCM lies - underneath the cover and none of the wires were corroded or damaged in any way.

Contacting some friends of mine to see if anyone can repair / diagnose my ECM as we speak - but other than that; still hoping it has to be something else.

 

It seems like most of your errors are from the Body Computer (BCM). And the ambient sensor could have been damaged during the engine swap.

The computer under the battery is for the power steering (EPS). With the EPS ECU incapacitated, the ABS and Trac will be disabled too.

I bet the fuse for the EPS is blown. It's an 80AMP inline fuseable link in the clear box by the battery. The fuse is section blown is just like a regular fuse with a Z link that opens if too much current is drawn or the battery has the polarity reversed. Take a look in there and report back. If the battery had the polarity reversed, there may be others. Oh, it's a buss bar, there are 14+ fuses all powered and joined in one strip. Blow one, replace the strip.