P1445&1446 Slow Down flashing

Those codes are telling you the car ECU is seeing a high temperature signal from the temperature sensor coming out of Bank 1 Cat Converter. Continued driving with those codes will cause the SDL to stay solid, and then the car will shut off bank 1 ignition causing loss of power.

Is it a DIY thing? Many of us have fixed this, but it is entirely dependent on how capable you are as a technician.

Find the thermal couple control module for bank 1, behind the right side rear wheel, mounted on a panel, see if it is Black or Green in color. If it's black, replace it with a new Green one. Reset the OBD codes, drive on to see if it comes back.

If it comes back, measure the temperature of the cat converter using a laser thermometer, compare that to the temp of the left side cat converter. If the difference is huge, you have excess fuel in the cat converter for bank 1. Now it's time to chase down the misfire.

 

Note that there are usually two Thermocouple ECUs in that location. One for the right hand (bank 1) cat thermocouple and one for the exhaust bypass thermocouple. I assume you're familiar with the exhaust bypass system and where to find the bypass valve.

Depending on what diagnostic work has been done on the system before, you may find plugs swapped over between these two. To make sure you are replacing the correct thermocouple ECU, follow the braided lines to the exhaust components.

Here are the locations of the two thermocouples on the right hand side... see (G)

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(T) is the exhaust bypass valve thermocouple. According to this diagram, the vertically mounted ECU is shown as the right hand cat ECU (but confirm this visually on your car)

Flashing at startup usually means that the thermocouple ECU is faulty, but don't exclude the thermocouple itself.

Cheaper, reliable aftermarket Thermocouples and Thermocouple ECUs are available from Technistrada.com. Before purchasing new parts, you may want to clear the fault codes and swap the left and right cat thermocouple ECUs to see if the fault transfers. Note that the Technistrada thermocouples are smaller than the originals. If you want originality, you may have to purchase OEM thermocouple ECUs.

Some of the workshop manual diagrams are can be misleading. They seem to be a hybrid of old/new/Euro/USA cars. I have slightly modified the diagram above to reduce the confusion factor.

 

Is you CEL light on?

 

The SDL will flash from cold if there is no signal from the EGT sensor (the Thermocouple) to the exhaust temperature Control Box. The absence of signal could be due to bad Thermocouple sensor or due to breakage somewhere in the sensor wires. Perhaps the first thing to check - try with swapping the Thermocouples left-right.

Of course, it could also be due to bad Control Box and possibly also due to poor contact somewhere along the signal wire from the Control Box to the ECU. Swapping the Control Boxes may also give you some indication of where the fault is.