Author Topic: Toyota Highlander Check Engine and VSC light, and code P0442  (Read 13099 times)

Offline goodfellow

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This problem occurred last evening as my daughter was driving home from work in her 2005 4WD Toyota Highlander. The check engine and VSC (Vehicle Stability Control) lights came on in traffic and the computer set a P0442 code (small leak in EVAP system).





Apparently this is very common code on older Toyota vehicles, and it seems to be the default code anytime there's vacuum or fuel vapor leak in the intake, fuel, and or EVAP system. Hence it's a pain to troubleshoot because it covers so much sub-system territory. The most common cause is a leaking fuel cap (either seal is bad, the plastic is cracked, or is not an OEM Toyota cap). Other causes could be the usual array of hoses, the purge solenoid, or the vapor canister underneath the right rear of the vehicle.

The cap looked good -- and the rubber seal was smooth. Hence I eliminated that possibility. The only other option is to thoroughly inspect the entire array of hoses and start looking for a culprit. A better solution is to smoke it with a machine --





I removed the air filter box and assembly and hooked up my DIY smoke machine and proceeded to smoke the intake first. At first I didn't see anything, but after adding a light bar -- I saw small whiffs of smoke coming from a hose on the top of the intake --

BTW -- this cheap HF light bar works like a charm. The extra light helped locate the source of the smoke.



Ironically, the hose in question is the same hose that attaches to the factory installed EVAP vent test fitting.



It had a very small crack about 1-1/2" long -- here it is after I took it off and spread it apart.



I installed a bulk piece of 5/16" fuel line hose in its place and secured it with two worm drive hose clamps.



Bottom line - the P0442 code covers a lot of territory, and in most cases it's just a simple hose or clamp that has gone bad on older vehicles. That said, finding the leak can take forever due to the many hoses, components, and connections in all the associated systems.

Per Toyota:  A P0442 could indicate a leak in the following systems

Missing or loose fuel cap
Incorrect fuel filler cap used
Fuel filler cap remains open or fails to close
Foreign matter caught in fuel filler cap
EVAP canister or fuel tank leaks
EVAP system hose leaking
Fuel tank leaking

There is a full explanation and excellent diagrams of the system and the P0442 code, at the following link....

https://parts.olathetoyota.com/p0442-code-toyota


« Last Edit: April 10, 2019, 02:25:06 PM by goodfellow »

Offline Heiny57

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Re: Toyota Highlander Check Engine and VSC light, and code P0442
« Reply #1 on: April 11, 2019, 04:43:41 PM »
Wow great catch Ray. That machine is paying off.
MAGA

If you can’t fix it with a hammer, it must be electrical.

Offline stokester

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Re: Toyota Highlander Check Engine and VSC light, and code P0442
« Reply #2 on: April 11, 2019, 04:52:50 PM »
Nice DIY smoke machine!

I've found that a good, strong white LED light is sometimes needed to see those wisps of smoke escaping from a bad line or component.  That HF underhood light looks nice, I'll have to check it out.
Nick
Yorktown, VA

Offline torqueman2002

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Re: Toyota Highlander Check Engine and VSC light, and code P0442
« Reply #3 on: April 11, 2019, 05:39:32 PM »
Good find and I'm thinking your machine will prove it's self very useful in the future as well.

As a engine controls service guy, it makes me wonder why Toyota chooses to turn on the VSC (Vehicle Stability Control) light too.

I once floated the idea of detecting EVAP leaks, by using a radio active gas and a Geiger counter. That didn't get too far, but it did some laughs.  :-[
"I got to show the young boys how not to do it. I haven't showed them everything not to do, yet. It's a big job!" - Otto Kilcher

Offline Matt_T

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Re: Toyota Highlander Check Engine and VSC light, and code P0442
« Reply #4 on: April 11, 2019, 08:27:57 PM »
As a engine controls service guy, it makes me wonder why Toyota chooses to turn on the VSC (Vehicle Stability Control) light too.

I doubt they chose to do it. Probably a bug. Or maybe one light was already on and the other one illuminating got them both noticed.

I once floated the idea of detecting EVAP leaks, by using a radio active gas and a Geiger counter. That didn't get too far, but it did some laughs.  :-[

LOL, but you might be on to something. A combustible gas detector would likely find some leaks unaided and pressurizing the system with a few inches of propane would find the rest.

https://www.mastercool.com/product/55975intellasense-iii-combustible-gas-leak-detector-hvac/

Offline goodfellow

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Re: Toyota Highlander Check Engine and VSC light, and code P0442
« Reply #5 on: April 11, 2019, 08:34:26 PM »
As a engine controls service guy, it makes me wonder why Toyota chooses to turn on the VSC (Vehicle Stability Control) light too.

I doubt they chose to do it. Probably a bug. Or maybe one light was already on and the other one illuminating got them both noticed.


That's what I thought at first Matt, but reading many similar P0442 related control issues on the web, it seems that both the check engine and VSC lights are the norm and not the exception when it comes to EVAP related problems. Like Torqueman, I'm having trouble understanding the systems logic behind that algorithm. 

Offline Matt_T

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Re: Toyota Highlander Check Engine and VSC light, and code P0442
« Reply #6 on: April 12, 2019, 12:03:06 AM »
Like Torqueman, I'm having trouble understanding the systems logic behind that algorithm.

It isn't logical. That's why I think it's a bug rather than a deliberate feature. My guess is a screwup in the PCM to VSC comms. The bit that used to be set for misfire got changed to evap BS or something along those lines.
« Last Edit: April 12, 2019, 12:25:38 AM by Matt_T »

Offline muddy

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Re: Toyota Highlander Check Engine and VSC light, and code P0442
« Reply #7 on: April 12, 2019, 08:08:58 PM »
Great catch if only those smoke machines work on electrical problems lolx

Sent from my E6910 using Tapatalk


Offline torqueman2002

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Re: Toyota Highlander Check Engine and VSC light, and code P0442
« Reply #8 on: April 12, 2019, 09:11:18 PM »
... reading many similar P0442 related control issues on the web, it seems that both the check engine and VSC lights are the norm and not the exception when it comes to EVAP related problems. ....
I agree GF, it's a Toyota related thing.

I talked with a EVAP calibrator for GM today, and he confirmed it is not an OBD 2 strategy used by GM.

GM does disable VSC on some OBD 2 faults, but not EVAP.

Sorry, I can't speak more definitively about Toyota's strategy.
"I got to show the young boys how not to do it. I haven't showed them everything not to do, yet. It's a big job!" - Otto Kilcher