Car was running fine, with no check engine light. All of the sudden the check engine light came on and the engine started missing. Idles OK, and seems to run OK at full throttle. Between idle and WOT, the engine misses badly especially while accelerating. Car shakes and surges due to engine misfires. Codes: P3002 P0304 P0300 P0303 P0302 P1636 12v battery tests OK Fuses look OK on right side under hood fuse box Inverter coolant level is OK Engine coolant level is OK Engine oil looks good. Any ideas? Thanks.
Check out this thread, for starters: 01 p1636 and p3002 | PriusChat Also, you can google "2002 Prius [insert trouble code here]" and get a bunch of hits.
You can often find a lot of information by googling, but often a lot of it is lousy. Those are all engine misfiring codes except the P1636. P1636 is set by the engine ECU if there was a period of 1.5 seconds some time when it wasn't able to talk to the HV ECU (that's kind of the orchestra conductor for the car). That's kind of interesting and maybe worth looking at later, but it isn't why the engine is misfiring, and the misfiring is bad. The usual drill for a misfiring engine, over all the years way before hybrids, is to make sure there is compression, fuel charge, and spark, happening at the right times and amounts. Spark involves checking the plugs and igniters and watching the ignition signals on a scope if you have one. Fuel charge involves checking the fuel pump pressure, the injectors, the airflow sensor, any possible leaks in the air intake downstream of the airflow sensor (upstream, the ECM can sense it and compensate, but downstream it just makes the mixture all wrong). Compression involves, well, a compression test, though in a Prius it can be easier to use a leakdown tester and do a leakdown test, which tells you the same stuff. If there's still a P1636 around after you've got the misfiring under control, the tests are for the wiring between the engine ECU and the HV ECU, or an actual problem in either ECU. Since the P1636 seems to have been transient (the two ECUs are communicating well enough for the ECM to know when the HV ECU wants it to start and stop the engine, and the HV ECU is working well enough to tell it to, and the ECM is working well enough to try to run the engine, notice the misfiring, and tell you about it), the explanation could be something like a glitch that interrupted their communication for a second and a half, once. You could clear and see if the P1636 comes back.
"You can often find a lot of information by googling, but often a lot of it is lousy." I was referring only to PRIUSchat posts cited on google. Of course, OP could always use the "Search Forums" function on this site to extract more information.
Regrettably, even some of the information here on PriusChat isn't always as helpful as you'd hope; I took a look at some of the other threads before posting. What seems to happen a lot is a car will show like five codes about misfiring and one that has something to do with a computer, and folks will jump to "the computer is hosed!" rather than following basic diagnosis. Usually the problem gets found and fixed quicker by paying close attention to what the reported codes really mean, including in this case that P1636 doesn't just mean something about a computer, it means there are two computers that talk to each other over wires, and at one point they couldn't do that for at least 1.5 seconds. Interesting to know and maybe worth tracing down to a cause if it keeps happening, but not if it gets in the way of solving the misfire issues.
