The TCS and check engine light both came on my 2002 honda odyssey? Is it the O2 Sensor? Or can I just reset the lights? The engine also idles very low when the vehicle is stopped at a traffic light. No problems when the van is driving engine rpms are all normal etc...

Plug in an obd reader to find out the reason for the check engine light! Could be anything.

i'd say a break in the wiring somewhere

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The tcs light will come on whenever the engine light is on, this is because the tcs cant operate correctly when engine is not running good so its shut down by the computer, the code if the only code means there a problem with the knock sensor, you will need to check the connection and make sure the wire is good and if it is then you will need to replace the knock sensor, heres a diagram to help you locate the knock sensor good luck, hope this helps,

Have it properly diagnosed by a repair shop,
and resolved

The following is from the Honda Odyssey (1999-2004) Service Manual page 19-81:

"When the Malfunction Indicator Light (MIL or check engine light) and the Traction Control System (TCS) light are both on at the same time, you should troubleshoot the Programmed Fuel Injection (PGM-FI) system first."

"The TCS indicator will come on if one or more of the following components are faulty:
heated oxygen sensor, manifold absolute pressure sensor, crankshaft position sensor, engine coolant temp. sensor, throttle position sensor, top dead center sensor 1 or 2, intake air temp. sensor, exhaust gas recirculation, barometric pressure sensor, idle air control valve, VTEC pressure switch, knock sensor, fuel supply system, automatic transaxle, and misfire detection system of the PGM-FI system."

Most major auto parts stores have a code reader that will read out your diagnostic trouble codes or DTC's that are stored in the car's computer when the MIL comes on. They will do it for free. With these codes, you can narrow down what is wrong. This is good information to have if you are dealing with a mechanic or dealership. The terminal to hook up the code reader is under the driver's side dash about in line with your right shin.

When the engine light comes on, the tcs automatically comes on too, until vehicle is re-started. Once you fix the issue with the engine light , tcs won’t come on anymore.

No, no need to go the expense.

There are several things that will turn the check engine light and TCS light on .If you get the code I can tell you exactly what the problem is . On your year i see transmission problems as well as EGR problems. If you go to any large auto parts store they will check the code for free or a very small fee.

i have 2002 honda odyssey
nowadys engine ang tcs light come on with P0131,0132,P0136,P0137