What could be wrong with my 2006 Honda Odyssey. It has no heat, but the engine is running hot. I thought maybe coolant level was low but overflow tank was right at max

I would say it is possible an overheated engine which is not coolling the transmission can trigger a lot of lights. Many transmissons are heated and coolled by a line which goes to the radiator of the engine cooling system.

Could be.. is the system FULL? Air in it can cause some odd things. When engine and coolant are COLD (as in after sitting over night), open the radiator cap. Top off the overflow res with a 50/50 antifreeze / water mixture to HOT mark. Start engine, turn heat to hot and fan to high. Top off RADIATOR with same 50/50 mixture slowly & gradually. As the coolant circulates, it should bring any AIR trapped in the system (from heater core & engine block) to the radiator where you can replace it with the 50/50 mix. Once the coolant is HOT and stays level - about an inch under the opening, close the radiator. Monitor the overflow res and add as needed. Good luck!

add coolant let it run til the thermostat opens to see where the level is at if you need to add more or not

check coolant level sound like engine low on antifreeze.make sure coolant overflow jug coolant level full cold mark.if overflow jug empty more likely radiator low on coolant allowing air in the cooling system.

first check coolant level in radiator coolant level sound low.if coolant overflow jug empty.coolant sysyem low, when add coolant to coolant overflow jug coolant level should stay at full cold mark.if coolant level okay,engine overheat while sitting or moving in slow traffic either coolant fan relay or fuse could be bad.or engine coolant temperature sensor could be bad. coolant sensor turn on cooling fan at certain temperature.hot wire check to make sure cooling fan motor not bad or short in wires.if all is good have pcm check it controls fan relay to through the coolant temperature sensor signal when coolant get hot.

ADD COOLANT IN THE COOLANT OVERFLOW JUG UNTIL COOLANT LEVEL STOP DROPPING AND COOLANT LEVEL STAY AT THE FULL COLD MARK.PLACE COOLANT OVERFLOW JUG CAP BACK ON JUG.CRANK VECHICLE UNTIL ENGINE START WARMING UP. STOP ENGINE WAIT FOR A WHILE UNTIL COOLANT COOL DOWN TO KEEP FROM GETTING SCALDED. USE A LARGE RAG OVER THE OVERFLOW JUG CAP OPEN OVERFLOW JUG CAP A LITTLE AT A TIME REMOVE OVERJUG CAP CHECK COOLANT LEVEL ADD MORE. COOLANT IN THE OVERFLOW JUG.THEN START VECHICLE AGAIN.LET ENGINE IDLE UNTIL TOP RADIATOR GET HOT.THEN THERMOSTAT WILL BE OPEN.WHILE ENGINE IDLING WATCH THE TEMPERATURE GAUGE IN VECHICLE IF TEMPERATURE GAUGE START CLIMBING IN THE HOT ZONE.TURN OFF VECHICLE LET IT SET A WHILE THEN USE LARGE RAG REMOVE OVERFLOW JUG CAP.ADD MORE COOLANT, PLACE CAP BACK ON START VECHICLE AGAIN KEEP DOING THIS PROCEDURE UNTIL TEMPERATURE STOP CLIMBING HOT ZONE.AND WHEN COOLANT LEVEL STOP DROPPING IN THE COOLANT OVERFLOW JUG.AIR IS OUT THE SYSTEM, BUT KEEP COOLANT LEVEL IN THE COOLANT OVERFLOW JUG AT THE FULL COLD MARK.DONT OVERFILL.DONT LET COOLANT OVERFLOW JUG RUN DRY IF SO AIR WILL ENTER COOLANT SYSTEM BECAUSE COOLANT LEVEL WILL BE LOW ENGINE WILL START OVERHEATING.

CHECK COOLANT LEVEL STILL LOW.ADD MORE COOLANT.UNTIL RADIATOR OVERFLOW FULL AT COLD MARK.THEN CRANK ENGINE UP LET IDLE FEW MINUTES LOOK DOWN COOLANT OVER FLOW JUG ADD MORE COOLANT IF LEVEL DROPPED.WHILE ENGINE RUNNING KEEP EYE ON TEMPERATURE GAUGE.WHEN THERMOSTAT HOSE GET HOT.TURN OFF ENGINE WAIT A LITTLE WHILE TO KEEP FROM GETTING SCALD TAKE LARGE RAG PLACE OVER OVERFLOW JUG RADIATOR CAP.OPEN CAP A LITTLE A TIME.IF COOLANT TRIES BOIL OUT.LET VECHICLE SET A WHILE LONGER.ADD MORE COOLANT.WHEN COOLANT LEVEL CORRECT AND ALL AIR OUT THE COOLANT SYSTEM.IT WILL STOP OVERHEATING.LONG AS ENGINE RUNNING HOT TURN OFF THE ENGINE POUR IN MORE COOLANT UNTIL COOLANT LEVEL STOP DROPPING IN RADIATOR.KEEP COOLANT LEVEL IN OVERFLOW AT COLD MARK.DONT OVER FILL OVERFLOW JUG.

If you dont have an external coolant leak anywhere under your hood that has shown up on your driveway it could be the intake manifold or the headgasket leaking. Also check the thermostate to solve the heat issue.

No heat is often a symptom of low coolant, usually followed by overheat. There are other controls that regulate heater, but right now, re-fill the cooling system with engine running and heater on high, then check for leaks (coolant you lost went somewhere...you need to determine where) Low coolant will damage your engine. Take care of that first, then if heater still does not work, then do diagnosis on that. (if you loose the engine heat won't matter, will it!)