Oops. Check Hybrid System after Intake Manifold/EGR Pipe Cleaning

I undertook this maintenance as a preventive measure, and to see if I could bump up the gas mileage a bit. After reassembly, when I try to start it up, the engine runs for 1-2 seconds, and stops, and I get a "Check Hybrid System" error. The engine will not restart. I'm trying to figure out where I screwed things up. Right now I might have to get it towed to a shop.

I bought the Prius used last month, and it's at 151K miles. I've driven it about 800 miles since I've owned it. It had been running perfectly fine, with no check engine lights or symptoms. The scheduled maintenance items were all caught up. I had spark plugs changed, engine coolant changed, transaxle fluid changed at the famous Luscious Garage several week ago, and they said the car was in good shape. They actually recommended NOT cleaning the EGR pipe/manifold/throttle body or replacing the PCV valve if there were no symptoms or check engine lights. They said not to worry about it until symptoms occur - probably to save money. Maybe I should have listened to them, but I liked the ideal of things running perfectly.

I used information from the "missing under light throttle" and other intake manifold cleaning threads and a couple pdfs on throttle body removal and intake manifold removal from the 2010 Toyota Prius Repair Manual that Mendel Leisk had attached to another thread. I generally followed the repair manual, except for not disconnecting stuff that didn't have to be disconnected, like the coolant hoses on the throttle body. That is to say, with the manual pdfs in front of me, I'm pretty sure I didn't forget to reconnect any connectors or hoses when reassembling.

A moderate amount of dry, sooty carbon material was in the EGR pipe. I cleaned that out. The port leading to the EGR valve assembly was also filled with that dry soot, and I cleaned that out with a pipe cleaner, used dry, since I didn't want to create a sticky clog in the valve. I stuck a vacuum cleaner to that port afterwards, in case I had pushed soot back towards the valve with the pipe cleaner.

The throttle body plate looked fairly clean already, but I did clean it up further with throttle body/intake manifold cleaner, and worked the plate open/close quite a bit while doing so (not sure that would cause a problem). There was oil visible in the intake manifold under the throttle body. I soaked that up with paper towels.

The main EGR passage in the intake manifold had dry sooty material on the side that the EGR pipe attaches to, and transitioned to oily sludge on the far end, though there wasn't a complete blockage. I cleaned the main EGR passage and the four smaller passages out with throttle body cleaner and pipe cleaners. The interior of the intake manifold was oily, so I cleaned that up best I could with throttle body/intake manifold cleaner and wiping through the openings with rags. I also swished the throttle body cleaner around the inside of the intake manifold by rocking and turning and flipping it around. At some point, I realized that there was a sensor still attached to the intake manifold immediately adjacent to the throttle body, and became concerned that I was contaminating it. I removed the sensor, and it was oily and probably covered with throttle body cleaner too, so I sprayed it directly with throttle body cleaner to clean it further. I figured it had probably been covered in oil before like everything else in there, so no harm done. But this is one of the main things that I suspect now as to causing the problem. I let it air dry (though maybe 90% dry) and put it back on the intake manifold.

The engine side was also oily, so I cleaned that up pretty well with a rag soaked in throttle body cleaner. I did reach in as far as I could get my fingers, and did touch the injectors, but I don't think I left any oil on them - I didn't that reach far in when getting the bulk of the oil out, just when cleaning the black deposits.

With the intake off, I replaced the PCV valve. It was oily on both ends, but was still clicked when shook. I also cleaned the oil out of the rubber hose that goes from the PCV valve to the intake manifold.

After reassembly, I started the car. After the engine ran for 1-2 seconds, it stopped and I got a Check Hybrid System warning. I kept driving on EV for 3 blocks before I realized that the engine wasn't going to restart, so I turned around and drove back home before the battery died. I think it has 1 or 2 bars now.

I have an ODBII bluetooth thing installed that I hadn't played around with much. I have a Windows phone, so I had OBD Auto Doctor (free version) installed. I hadn't found it useful until now. After the Check Hybrid System error occurred, I paid $10 for the app upgrade to be able to clear DTCs with it. I then followed the procedure in the Repair Manual for what to do after throttle body reassembly: a) disconnect cable from negative battery terminal, wait 60 seconds and reconnect, b) clear DTCs with OBD Auto Doctor (instead of Techstream), c) set vehicle to inspection mode (used the 2x accelerator pedal in P, 2x accelerator in N, 2x accelerator in P method). In inspection mode, I get the same problem: the engine runs for 1-2 seconds and then stops and I get the Check Hybrid System error. I disconnected the battery 2-3 times and tried this several times, only the last time in inspection mode.

Theses are the DTCs under confirmed and pending:
P0123 Throttle/pedal position sensor/Switch "A" circuit high
P2135 Throttle/pedal position sensor/Switch "A"/"B" voltage correlation
P2135 Throttle position Sensor 1-2 correlation

These DTCs are under permanent:
P0102 Mass or volume flow "A" circuit low
P0113 intake air Temperature Sensor 1 circuit high (bank 1)

Can anyone provide suggestions on what to do next? What is that sensor next to the throttle body that I was playing with - maybe the intake air temperature sensor? I can't find a part of that name on the Toyota Online Parts catalog. I'm in San Jose, not Alaska at this time. Anyone local that can help? Or is there a close recommended shop I can get it towed to. The various garages on Winfield Blvd are fairly close.

 

DOH! I visualized how I reassembled everything last night and realized that I might not have plugged the big connector back into the throttle body. I went out to look at the car, and, sure enough, that was it. I was reassembling outside in the dark by headlamp, so I missed that, and I missed that in the repair manual pdf.

Now the car is running better than ever. I haven't been keeping good records, but I think I had only been averaging about 45 mpg in the ~800 miles that I've had the car, with semi-hypermiling required to get about 49 mpg. My best was on the drive home from Alameda to SF to San Jose the day I bought it, when I recorded 57.7 mpg (MFD) for the very conservative/hypermiling first drive. I had attributed the lower mileage to my shorter trip lengths in general, but I knew the car should have been capable of better. Now after yesterday's work and plugging in that connector to the throttle body, I reset the trip odometer and drove the car around Almaden neighborhood in San Jose. This was after warmup, but I was seeing the average mpg go from mid-60s to 75 mpg on the flatter parts, and it dropped down to 58 mpg average overall for 6 miles after driving through some hilly areas. Seeing 60s and 70s on the display was unheard for me with this car and even over about 50 mpg was rare and only seen once for that first drive. Now it's probably at least 10 mpg better than I would have seen for that trip before all that work. Awesome.

 

Luscious Garage suggested inverter coolant too, but I declined because it was changed when a new IPM was installed in the inverter at 127K.

I noticed a sharp decrease in documented front pad thickness when I was carefully going over the maintenance records in the Toyota Owner's site, so I wasn't surprised when front pads were gone. A local shop put in new front pads, turned the front rotors, and lubed both front and back brakes. Back pads are fine. The sharp decrease from an initially slow decrease suggests that maybe the front brakes started dragging or something, all before I owned the car of course. I know it's more common for the rear brake sliding pins to lose lubrication, but that's my guess.

 

Yes, I'm getting it into tip-top condition for a car with 151K. That was the plan from the start - looking for a high mileage car with a lot of life left to keep it lower cost. I have a checklist of stuff from very minor to bigger that I've done on the car, and I've gotten about 30 things checked off so far. All the mechanical stuff is now done. All that is left is cosmetic like touching up paint scratches and polishing the headlights.

My driving mileage is generally low, so I probably won't hit 300K unless my future commute or habits change, but I'm probably going to keep this Prius for a relatively long time. My other car is a 1996 Subaru that I bought in 2000 with 137K miles, and it only has about 207K miles on it now.

Thanks. I had that thought briefly before I started, but wasn't really regretting anything. I knew that whatever was wrong was probably not a costly thing to fix. The seemingly random/unrelated to my work DTCs made me think that maybe I did leave something unplugged, so I starting visualizing what I had done and not done and figured it out in my head before even opening up the hood again. I should have had that thought process before posting here.

Based on the Toyota owner's site, I knew the previous owner had brought the car into the dealer complaining that it was only getting 35 mpg at 149K only 1,000 miles before selling the car to me. To pass smog, he need to replace the MAF, purge valve, and A/F sensor. That brought it up to the about 45 mpg that I have been getting. The spark plug change ended up not helping the gas mileage. Based on the stuff I've been reading on Priuschat, I figured that at 151K miles even without obvious symptoms like knocking/hesistation, etc., the EGR, intake manifold, and PCV were probably also filled with soot and greasy slop to some degree, and therefore the likely culprits for the still lower gas mileage. That seems to have been true. I just joined fuelly to track gas mileage now that it seems to be pretty respectable.

 

Oh, that seems to be on the low mileage side. There isn't much talk about HV batteries in the Gen3 forums yet. I figure that even with a HV battery change, I'm way ahead buying used. My Prius is a IV with the Solar package, so the original owner probably paid $30K+ at the time, plus what he paid to keep it running and repaired. After my fixing it up, it will be a very similar visual and mechanical experience for the next 5 years to what the original owner experienced during his 5 years. And it will have cost me in the $9K range for the purchase and initial fixing-it-up-best-I-can stage. My operating costs should be similar to the original owner for the most part, except maybe an HV battery. But the original owner paid about $1400 at the dealer just to get it to pass smog check for me, so that's about half an HV battery there. He probably could have saved a lot going to an independent shop like Luscious... or doing some of the stuff himself. And after 5 more years, my car will probably still be worth around $5K? judging by 2005 Prius with around 200K miles.

For estimating purposes, I have the HV battery lasting about 10 years or 200K-300K+ miles, whichever comes first, so I think it should be good for about 5 more years with my lower mileage driving, but I won't complain too much whenever it fails.

I did not pick up on the oil consumption threads before buying, so I hope I don't and won't have that problem. Head gasket replacement sounds expensive. So far, I haven't noticed oil consumption. I'm used to checking oil in my Subie, that is of a vintage that doesn't have head gasket problems, but has oil leaks of lesser concern - so I'll keep up that habit.

 

Well the first 4 years of a car is exempt, but afterwards Prii do have to pass smog since Spring of 2015 in California. The techs plug into the OBD and do a visual check of the emissions system (check the gas cap and ?). The check engine light can't be on, and all DTCs and readiness codes have to be clear.

The seller of my car had the check engine light come on before doing the smog and then again before doing the recheck. So that meant a couple trips to the dealer for him, and several days of driving afterwards each time so that the readiness codes would clear.

 

Yup, I knew where the MAF was to start. It's in a very clean location and sees only clean air. The vacuum pressure sensor is in a place that gets very oily in Prii, so hitting it with throttle body/intake cleaner turned out to be perfectly OK.