B1498 Communication Malfunction A/C Inverter Local

The compressor receives an inverter control signal from the power management ECU. I am guessing this is the communication malfunction you are experiencing. The ECU talks to the A/C amplifier assembly for data input. Check those connections and also confirm that the coolant is completely cleaned from the comm port.

 

I know this thread is old but were you ever able to resolve your issue? I had my engine replaced recently and I'm getting this code now.

 

Well, this is now another person wondering about this code.... I did a head job and during that, some coolant briefly dropped into the control connector of the A/C compressor. Now I have a 1498 error too. I never had that before. I wouldn't think that having fluid temporarily drop into the connector would cause a problem. They are usually sealed and I definitely cleaned everything out and ensured it was dry before reassembly. But now the compressor turns on for a bit and then turns off and throws the B1498 error.

Does anyone know a way to fix this? What is the problem? Did the internal inverter board somehow get fried?

 

If the connector was disconnected when the spill occurred, there could be coolant residue on the connector housing, terminals, or inside the unit, causing a poor connection or intermittent terminal-to-terminal or terminal-to-ground faults. Before replacing any expensive parts, try throughly cleaning the connector.

You could also try steps 1 through 5 of the troubleshooting procedure for DTC B1498/98 in the Air Conditioning System section of the Repair Manual (more info). This procedure includes checks for CAN or hybrid control system DTCs and for wire harness faults.

 

Thank you for the response Elktroingenie.... I really do appreciate your taking the time you took to add some ideas....

I immediately removed the coolant that splashed in there and blew it clean. Two weeks passed while I was doing my head job, and then everything went back together. With about 2000 miles on the car, it started to get warm outside and that is when the A/C issue cropped up. I went back and confirmed all connections and did take an extra step of thoroughly cleaning the connection. I used an electronics aerosol on both the compressor and the connector, and lightly drew a needle file across the pins to break any crud that could have been there. The problem remained, but I really think the connection is fine now. I also opened the connector on the wire side to see if there were any crushed wires; there were none.

I do have a little more information though. I've been trying to correlate what might trigger the problem or be related. This morning (very cool), the A/C worked perfect and the sight glass shows proper level (that was confirmed by an independent shop, by the way... they said there is no leaks and it is all charged). I jostled the wires around to see if there was a position where everything stopped... Again, no problems; it blew fine.

Now the observation. Yesterday when it was hot, I noticed that the pump was on when the fans were on, and the opposite was also true. As soon as the fans stopped, the pump stopped (or shortly thereafter). This morning it was very cold and the fans were on the whole time the pump was on (after 5 minutes of having it on, I gave up... never did fail). Part of me is wondering if I'm on a wild goose chase. Maybe this B1498 (which I've not seen on my cheesy FixD OBD reader, the independent shop told me about that... oh, and yes, I'm getting a better reader) is tangential. Maybe the lack of a fan causes the pump to heat up and go into a thermal shutdown. That would then cause the communications to stop and, therefore, the B1498. I'm wondering if that is possible... Thoughts?

I do know that this morning, the vertical aluminum bulb that is in the compressor line (not sure what this is... an expansion chamber) was *very* warm, along with the pump. But this morning, all of that was very cool. Now, it is true that the temperature outside was warm and it was, as stated, cool out this morning, but the mechanical compressing of the freon will generate a lot of heat. If the evaporator coil isn't getting air drawn through it to cool the freon down, then that heat is going to stay in the system.

Assuming this seems like a plausible scenario, I'd love to hear how one might diagnose the root cause of why the fans would not come on when the A/C pump is on. Sadly, I suspect the opposite is also true though. The ECU may shut the fans off if it detects a communications issue (B1498). I am aware that this whole vein of thought has two avenues of what is affecting what.

P.S. Thank you for the suggestion on the diagnosis steps and such. I became aware of the temporary TIS subscription just recently and I very well will try that route. Because it is time limited, I need to be sure I'll have a block of time to make use of the resource before it expires. But that is on the agenda if I cannot otherwise figure this thing out.

 

Slight update.... I'm working at home for my real job now, which gives me the opportunity to run out between meetings and to see if I can draw some conclusions about when the A/C works and when it does not.....

As I mentioned before, the compressor worked perfectly this morning when it was very cold. As such, I was very curious to see what would happen as the weather started to warm up. Sure enough, I pressed ON and the the engine, fans and A/C all came on. Eventually, the engine turned off (normal) and the radiator fans continued to run, as did the AC compressor. I could see fluid passing the sight glass and the low side was crispy cold...

And then..... The fans turned off! I could immediately hear the compressor turn off, and a visual inspection of the sight glass no longer showed fluid moving past. For a very brief moment, the fans came on again (and the fluid flowed in the sight glass), then the fans turn off, yada yada yada.

So, the conclusion is that when the fans are on, the pump is on. What I don't know is which behavior is causing no A/C. Is it an issue with the A/C compressor (B1498?) that turns off the compressor *and* thus the fans? Or is it the fans turning off for some reason that causes the ECU to say "wow! we don't run the A/C without the fans running, so I'm turning off the compressor".... Or, is there some electrical issue (relay, wiring, etc) which is influencing/causing all of this?

I can say that I've moved the wires around along the length of the harness to feel pretty confident in saying that I don't think there is an issue with the wiring (yes, I know this is not definitive and I will eventually check the continuity when I get time and if there is no other resolution).

Again, one final consideration here that I mentioned before. I have not personally seen the B1498 error. Further, when I press REC plus AUTO and START (no foot on brake), I get a flashing '00' on the temperature temp control. I understand that this means I have *no* codes. I was only told about the B1498 by a competent independent mechanic to whom I gave the car in an attempt to resolve the A/C issue. He eventually said that he could not figure out what was going on, but he was confident that the pump was working (although that doesn't mean there isn't an intermittent issue in the pump's inverter control board) and, more importantly, that the system was charged and not leaking. But the point is that I don't want to draw too much focus on the B1498. I think that my last scenario where a thermal overload within the pump could very well be true....

So, that is about it for now.... I am curious to hear if it is normal for the A/C to come on/off (as well as the fans) when the A/C is set to AUTO and LO. What I'm getting at here is... Maybe I really did have a connector issue and I've resolved that, and now the system is just behaving normally? I've owned the car since new (10 years), but I've never paid attention to the nuances of the A/C compressor.

 

Man, I did that thing that drives me crazy: people find a solution and don't post back about it.

Sorry about that.

In my case, the compressor didn't work at all and it had to be replaced. At the time (Aug 2018), it was about $125.

 

Thanks for posting!

Man, if I could a compressor replaced for $125 I'd do it just to see if it worked. But the compressor now is about $1300 (new.... $500 remanufactured, $150 as a gamble from a junk yard), $300 for Toyota's oil, and about $40 for an equivalent, and about $125 for the charging of the system. That adds up to enough that I want to be sure I really need to replace it first.

 

Ah. Yes, that can be normal behavior. It's more normal when set for AUTO and a temperature than when set for AUTO and LO, though.

The compressor is variable speed. Depending on how hot it is outside and how much cooling you're asking for, if you have a scan tool to watch the "AC watts" parameter, you could see the compressor running at over two thousand watts full out, all the way down to maybe 250 or 300 watts when only a little cooling is needed. If less cooling is needed than that, it will cycle off and on (so, between 0 watts and 350, 450 or so).

If the fans aren't needed for engine or inverter cooling, they will also cycle off when the compressor does.

I am a little more puzzled that the compressor would be cycling off when the temp is set for LO. But this could happen if the evaporator temperature (another parameter you can watch with a scan tool) gets down to the range for potential icing, or if the liquid-line pressure (another watchable one!) goes out of bounds.

 

Fantastic information, Chapman. Thank you!
I don't have a scan tool, unfortunately, but I do have one on order. Because I'm not a professional mechanic, I cannot really justify a commercial grade unit. I currently have a FixD type which is completely inadequate for higher level stuff like what we are talking about. However, it works *really* well for increasing confidence for when my daughter or wife are using the car. They know/care little about mechanics, and if the service light goes on, this way it will immediately alert me wherever I am. I can see it and tell them that they really do need to get off the road because the water pump failed (type of thing).

I have an OBDLink MX+ on order, and it should be here in a few days. That should allow me to do some 'live' testing as you are suggesting. This is actually where I am going with it all too. I think I may really have had a poor connection in the connector before, but everything might be working perfectly now. My wife drove the car to school yesterday with LO and full fan. On the trip to school, the A/C was on and cranking cold air like there was no tomorrow; that trip was about 13 minutes. On the way back, however, the A/C stopped and she had to open the windows. That still doesn't feel "correct" to me, but I do have to note that the car was in ECO mode too. I have learned that this can affect the A/C compressor "on" times too.

I have yet to see the B1498 myself. I suspect the FixD is not capable of showing those, and my other OBD units are all pretty sketchy. The MX+ will hopefully resolve that hole. But I *would* expect a 14 and 98 to show up on the temperature display, assuming the REC + AUTO trick works on a 2012 Prius V heating system.

 

As I understand it, ECO mode puts a cap on the top power the A/C will run at. So in ECO mode, instead of running flat out under high demand, it will run up to around two thousand watts or so. I don't think ECO mode does anything directly with cycle times.

You shouldn't expect a 14 and a 98, just a 98. The display shows two-digit abbreviated versions of DTCs. For the HVAC, they all happen to be the xy digits of a corresponding B14xy DTC (I think). So if you ever saw a 14 and a 98, that would mean you also had a B1414 code (which isn't a thing ... at least in my Gen 3 liftback manual).

One thing not to get too excited over, if you ever see it, is 21 (B1421) ... that just means there's not much light shining on the dash top photosensor at the time you ask for codes.

Be thankful you're not working on one of the other systems, like the brakes, where the two digit abbreviations are not just the last two of the DTC, or sometimes are and sometimes aren't (like C1336 has blink code 98)!

Reading parameters like liquid pressure, AC watts, and so on, doesn't necessarily take a fancy scan tool, just one that you can teach the corresponding PIDs to. The smartphone app Torque is an example. You can find files with the Prius-specific PIDs in Torque's import format.

 

Thanks for the info on the expected digit display on the temp control. I had assumed that I'd see a fast flash of 14 and 98, then a long pause, repeat. But it makes sense that that they'd leave off the 14, I guess. At any rate, all I've seen is 00. I don't know if/how those codes get reset through the approach we are discussing for viewing. Maybe it is just when you turn the car off again?

I think you can get Torque to work on the FixD, but I don't have that app yet. It is good to know that a fairly inexpensive OBD will work with a more capable program though. I've gone through my share of ELM type OBD and I'm pretty fed up with them. Some may work fine, but I've not had good luck. This is why I bit the bullet and decided to get a MX+. They seem to have a fairly decent set of reviews on different sites, and at least I'm buying something from a "real" company. Most of the ELM guys are all weakly rebranded products from some shop in China for which there is no/little traceability. Been there, done that....

 

Tech stream with cable. Check ebay.
It the toy software toy dealerships use. Under $50

 

I wanted to give a quick update....checked for broken wires and could find none. After cleaning the contacts, things worked better, and that is a tell. Given this experience, and that of the original poster to this thread, I have come to what I believe is the likely problem.

The compressor is actually a neat device. It has a variable frequency drive (VFD) board inside it so that the ECU can control the amount of power being used by the compressor. That is cool, but the problem is that the idiots at Denso appear to have used a connector that doesn't have the pins molded into the plastic (my theory). In addition, the connector is upwards facing. This means that *any* fluid that happens to drop on the connector can leak into the top part of the compressor where the VFD is located. That is an inexcusable weak point, in my honest opinion. Sure, you shouldn't be splashing coolant around, but you also build something with a defensive posture in mind (or you should).

Anyhow, I believe that coolant is not a very good dielectric and I suspect that even a small amount of coolant will drop onto the board and cause issues. Now comes the interesting thing... How to fix this (again, assuming I'm right).

The *best* solution would be to remove the top cover and you could easily clean the board. Unfortunately, although the VFD board is clearly not pressurized, the connections to the 3 phase motor have a rubber seal around them that press against the board. Without having taken a compressor apart, I am guessing that when you take off the cover, you'll relax the pressing of that seal, and all your R134a will quickly escape (and cause havoc on the environment, so don't do it!). So, the only option is to try to dilute/clean the board by introducing more fluid. Therein lies the conundrum. The best thing to do is to use a PCB or contact cleaner. But these are high VOC fluids, which means that they are flammable. Because they are being introduce into a closed cavity, they likely won't flash off very much, so the VOCs will remain. Technically this could even be a tiny bomb if you filled the thing up; however, I'm guessing we are talking about literally a tiny drop, which I seriously doubt could blow off the cover at all (worst case scenario).

Probably the best thing would be to evacuate the system, remove the cover (spoiler: you need to figure out how to remove the special bolts), clean everything, reassembly and then charge again. But, the reality is that I'm not even positive that the fluid can leak through the pins. Therefore, I went ahead with the "fill the connector with contact cleaner, wait 10 seconds, then gently blow out the remaining fluid into a ran (careful... don't want it in your eyes, etc). At the very least, this helped clean the contacts (I also used a tiny file to draw across the pins... not to file but to break any corrosion that might be there). If the pins are embedded, then nothing got into the cavity. If not, then a tiny amount did. And, if by chance my compressor fries, well, I'll have to get a new one and recharge anyhow. There isn't a huge downside to the experiment.

So, what are the results? So far, the car seems to no longer have an issue with the AC. It hasn't been driven extensively, and the weather has gotten a lot cooler more recently so the need for AC has been reduced. But, while I was using the AC, it didn't stop at all. Previously, I would run into problems within 15 to 30 seconds (or the compressor wouldn't even come on). Is this success then? I don't know... ONly time will tell.

Finally, there is near zero information out there about the Denso pumps. There is a single, and interesting, video of a guy taking apart a Denso AC pump on YouTube but, sadly, he doesn't really show much of the VFD board.

Full disclosure: I am an amateur and a flaming idiot. Don't trust anything I say or use this as a recommendation... If you decide to review my thoughts and take action on them, you do so at your own risk. I assume absolutely no responsibility or liability. I'm just an amateur bloke that is postulating how some of this MIGHT work.

 

I am pretty sure there's a thread here where somebody worked on that. If I remember right, there was frustration involved with the slack available between the connector and board, or board and motor, or something; anyway, a challenge to usefully disassembling without cutting or desoldering something.

Sometimes, another pair of eyes can help. After all, they had to have a way of assembling the thing.

 

I'd be really be interesting in that thread if you can remember more about it. I tried a bunch of different search terms, but I couldn't find anything. :-(
I can only judge what is inside the compressor by looking at the one video. But, I can definitely disconnect the HV line from the compressor. I did see some evidence that the board is mounted to the cover, but that isn't a huge issue. The three phases of the motor appear to be a pin arrangement. This is the area where I suspect the seal will be broken and the R134a will escape (and, which pretty much halts any idea of opening the compressor). If *that* came apart *without* allowing the coolant to escape, I'd happily take the top off. I don't care that the board might be riveted to the cover. I just need to be able to direct some cleaning spray onto the area directly below the LV connector.
It is almost worth buying a compressor from a junk yard. The problem is that there are no appropriately aged Priuses in stock right now in the local yards.

 

Hello bro i have the same as your problem please if you know the reason