I got tired of seemingly all error lights on the dash being blamed on a loose gas cap in particular by dealers. Seems to me a standard way for them to blame the customer and make them go away for a while.
That's even the excuse the Subaru dealer gave my mom when her Cruise control wouldn't work!
So today I loosened the cap to see what lights would come on. None did. I added ten gallons of gas and will give the ECM a few more days to "discover" the problem.
Anyone ever heard an explanation of this that would satisfy this electronic engineer with years of mechanical experience? And I don't mean some service writer's BS.
It doesn't make sense to me. How could a loose fuel cap trigger alerts that points to VSC, ABS, 4WD and Brake Lights. Toyota's diagnostic software must be going nuts.
So today I loosened the cap to see what lights would come on. None did. I added ten gallons of gas and will give the ECM a few more days to "discover" the problem.
Anyone ever heard an explanation of this that would satisfy this electronic engineer with years of mechanical experience? And I don't mean some service writer's BS.
I understand that the ECM only periodically runs a test of the fuel system integrity (vaccuum). So give the loose cap scenario some time and you should get a DTC light from lack of vacuum.
It doesn't make sense to me. How could a loose fuel cap trigger alerts that points to VSC, ABS, 4WD and Brake Lights. Toyota's diagnostic software must be going nuts.
My thinking is it's all a product of the over-reactive era we live in where we need to be protected from ourselves. Everything's a disaster and a big light show is more likely to get you to the dealer than one little oil light (which IS a disaster). So the software is purposely written to generate alarm. Apparently there is no logical cause and effect.
Reminds me of when a car owner's manual actually had useful maintenance info and owners were considered smart enough not to drink the antifreeze, oil or gasoline, without 17 pages of warnings.
I understand that the ECM only periodically runs a test of the fuel system integrity (vacuum). So give the loose cap scenario some time and you should get a DTC light from lack of vacuum.
Well the sensor, if any, would have to test for both vacuum and pressure altho pressure isn't likely to be a problem in the 0-20 degree temps we've been having in CT.
To hasten the process I'm also testing my '06 Accord in parallel.
Consider this:
The CT emissions test on OBDII vehicles has two parts. First they check for codes. None and you pass that part. (Some people whose cars have issues simply reset any DTCs at the emissions station. If they stay off for a few minutes they pass. Others have no clue and take a car in with the CE light on!)
The second part is removing the gas cap and pressure (& vacuum?) testing it on an air pump apparatus. So, if a car's ECM tests for fuel system integrity and sets codes why would they test the cap?
Dr Dyno, I think the test is for those vehicles that may not have an internal diagnostic for cap integrity, with the thought being that the high volatiles in gasoline are the ones that are most significant in causing smog. Also, maybe Hoover had manufacturered too many vacuum cleaners and in the course of their fire sale, someone said "let's use them for an emissions test!". Likely as anything, I guess.
The leak detection system sets the DTCs. However, not all DTCs are hard set immediately. Some need multiple instances before you will see a light. On some OBD test sets you will see these as 'pending' codes. They will go away if the problem does not persist. If you were to remove the gas cap, start the car, shut it off, and restart - you might see a hard set light.
BTW, if the dealer is blaming the gas cap they would need a specific DTC code that points in that direction. The next time you see the lights on, go to a local auto parts store and have them pull the codes (usually free) that are set.
I got tired of seemingly all error lights on the dash being blamed on a loose gas cap in particular by dealers. Seems to me a standard way for them to blame the customer and make them go away for a while.
That's even the excuse the Subaru dealer gave my mom when her Cruise control wouldn't work!
So today I loosened the cap to see what lights would come on. None did. I added ten gallons of gas and will give the ECM a few more days to "discover" the problem.
Anyone ever heard an explanation of this that would satisfy this electronic engineer with years of mechanical experience? And I don't mean some service writer's BS.
Thanks guys for the replies. I did a little more research. Here's what I found with a google search (on which my topic made #7!) Guess I better watch out for some Obamabot to come knocking especially since our new governor is also a Democrat!!
rav4two said:
Dr Dyno, I think the test is for those vehicles that may not have an internal diagnostic for cap integrity. . . Also, maybe Hoover had manufactured too many vacuum cleaners and in the course of their fire sale, someone said "let's use them for an emissions test!". Likely as anything, I guess.
Correct except that the test is for pressure so Hoover missed out.
From this CT emission testing evaluation report: http://www.ct.gov/dep/lib/dep/air/v...008-2009__june_25__2010_with_2009_im_data.pdf
"Gas Cap Test: Vehicles fail if their gas cap cannot hold pressure. Beginning in November 2004, only pre-1996 light-duty vehicles receive gas cap tests. The OBDII system adequately tests a vehicle‟s evaporative system on most 1996 and newer vehicles."
arries289 said:
The leak detection system sets the DTCs. However, not all DTCs are hard set immediately. . . If you were to remove the gas cap, start the car, shut it off, and restart - you might see a hard set light.
]The leak detection system sets the DTCs. However, not all DTCs are hard set immediately. . . If you were to remove the gas cap, start the car, shut it off, and restart - you might see a hard set light.
If the later happened why wouldn't we get a DTC every time we filled up?
If you start the car and run it with the cap off, stop, and restart again, maybe. You say you have a code reader. Did you pull any codes when the lights came on?
The leak detection system sets the DTCs. However, not all DTCs are hard set immediately. . . If you were to remove the gas cap, start the car, shut it off, and restart - you might see a hard set light.
Did a little more study on my RAV4 DVD. There's an Emissions block diagram showing the components but no explanations, so we have to figure out how they could work. Anyway one of the components is a "Refueling Valve" on the charcoal canister. It must give the system a timeout? when the cap is removed. Other components connected to the ECM are, the Purge Valve, and inside the Canister Pump Module, a Vent Valve (solenoid), a Leak Detector Pump and a Canister Pressure Sensor. The only test procedure I could find was pressurizing the system to 4kPa, (.58 psi) to check for leaks.
So the ECM must use the Canister Pressure Sensor and Leak Detector Pump to do a leak test. But there must be some temperature cutoff (measured by the engine intake temp sensor) otherwise we'd get the summertime pressure release hiss when removing the cap in winter. I suspect that's why I'm not getting any reaction from the system during winter. The system doesn't expect any vapor pressure and therefore doesn't test for it.
arries289 said:
If you start the car and run it with the cap off, stop, and restart again, maybe. You say you have a code reader. Did you pull any codes when the lights came on?
I assume you are referring to the VSC, ABS, 4WD and Brake lights from my other thread. No codes at all. They seem to be going on and off just as irregularly with the cap lose as with it tight.
So the question remains: What lights and codes do we get for a legitimate gas cap failure? In other words, when the dealer tries to blame the customer for not tightening the gas cap, what dash indication do we ask him we get, and what code he got that indicates we are at fault. I also doubt this issue ever happens below a certain air temperature.
The way I understand this is, manufacturers are required to make cars that don't vent gasoline into atmosphere. Which means a sealed fuel system, tank, lines, gas cap, etc.
The evap canister is used to trap fuel vapours (perhaps due to daily temperature cycles?) and draw air into the fuel tank to replace spent fuel (so they say, I can't vouch for this).
This system somehow operates at both very low temperatures, like -30, at which fuel vapour pressure is low, and at resonably high temperatures, when you leave the car in the sun.
"Health" of the system is monitored somehow, perhaps differently by different manufacturers, one option is pressure sensor in the fuel tank or evap canister, it can give off dtc's when gas cap is open.
You don't get fuel vapour hiss when you open the gas tank precisely becase of evap canister; Yet all ar manuals tell you to open cap carefully.
There could be some other way to track evap "health" that doesn't care much for open gas cap most of the time.
As I recall, the recommendation is basicly keep the gas cap closed, or your evap control might get confused (we told you, so that government doesn't blame us).
Took the Honda out tonight. After about ten miles the odometer flashed these words in sequence "CHECK" "GAS" "CAP" but still no response from the RAV4.
Okay, I give up! Its been 2 1/2 weeks with adding 5 gallons several times and still no CE, no codes. Since I have the other error lights issue http://rav4world.com/forums/viewtopic.php?t=28831 I may be introducing two variables. Remind me to retry the gas cap test after the speed sensor issue is resolved.
Okay, I give up! Its been 2 1/2 weeks with adding 5 gallons several times and still no CE, no codes. Since I have the other error lights issue VSC, ABS, 4WD & Brake lights on, no CE, no codes - Toyota RAV4 Forums : RAV4World.com I may be introducing two variables. Remind me to retry the gas cap test after the speed sensor issue is resolved.
Okay, since the ABS wheel sensor has pretty much gone away I rerunning the loose gas test. We'll see if summer weather wakes something up from it's apparent non-responsive hibernation last winter.:shrug:
On my 2004 2WD Sport the VSC, TRAC and check engine lights will light sometimes. If I tighten the gas cap when this happens, these 3 lights will go out.
I used the jumper wire trick on pins 4&13 on the OBDII connector. Turn the key to on and count the flashes. The procedure is in the service manual (sections BC-64 & CC-22). It says the VSC 51 is "Engine control system malfunction" and Cruise 69 is "Brake system malfunction." I still don't know what a check engine code 94 means.
James
________________
2008 Limited V6 2WD
"The Silver Bullet"
I used the jumper wire trick on pins 4&13 on the OBDII connector. Turn the key to on and count the flashes. The procedure is in the service manual (sections BC-64 & CC-22). It says the VSC 51 is "Engine control system malfunction" and Cruise 69 is "Brake system malfunction." I still don't know what a check engine code 94 means.
Thanks James, I had no idea that those codes even existed. It looks like you have been spending a lot of time reading the service manual.
I was expecting to see the codes like Dr.Dyno had (P0441 & P0445). That is why I was surprised to see your codes.
I guess you expected the "Engine Control System Malfunction", but is your "Brake System Malfunction" a real problem (perhaps an old problem that was stored in memory), or did that code pop up because Toyota disables ABS, Cruise, and other systems whenever it finds an engine problem.
I expect all the lights will go out after a couple of more driving cycles.
Rick, James probably got that procedure when it came up in another thread. But that thread didn't involve a set CE light because they come from the ABS computer not the "main" one which does set the CE light.
James, I expect Rick is right, those are old codes which can be reset by tapping on the brake pedal 8 times right after turning the key on with the jumper in place.
I'm betting you'll get codes similar to mine if you use or borrow an OBDII reader from an auto parts store.
OK, this morning the lights were still on and I was getting tired of looking at them so I reset the codes.
No need to disconnect the battery. Went to the driver's side fuse box under the hood. Pulled the EFI MAIN fuse (20A) and the ETCS fuse (10A) and waited 1 minute. Put them back, started the car, and the codes are cleared-no more lights. And I didn't have to reprogram the radio!
Please forgive my question if it sounds stupid but I'm a female and am not sure how to do much in way of car repairs. Where do I find the fuse box you mentioned? Did that resolve your problem with the lights for good?
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