maxnewbie

I pulled some codes after being unable to correct my low idle problems (500 RPM). I had cleaned out the TB and replaced the fuel filter and still experienced low RPMS (rough idling). I pulled the following codes:

0705 Evap system leak
0304 Knock sensor or circuit failure
0504 A/T control unit

I think the EVAP system leak is triggering the other two codes. I need assistance with this please! Do I have to replace the EVAP canister? Does anyone have experience with this specific problem?

njmaxseltd

iTrader: (19)

0705 - Check your gas cap. It may be defective.

0304 - You say your car has been idling low giving you a rough idle. The rough idle is probably whats tripping your KS circuit. Fix the idle problem and I bet your KS code (0304) goes away.

0504 - You may have a problem there. A few guys on here, including myself have gotten that code and have had to get new ECU's. Thankfully mine was still under warranty.

maxnewbie

Why just the gas cap? Haynes manual states that it can be a defective canister purge control valve, damaged canister, split or cracked hose(s) etc.

elcid

I got code 0504 and when I reset it went away and hasn't returned yet it's been about 3 months

dwapenyi

iTrader: (3)

Check the gas cap b/c it is part of the emissions system, and its a simple fix. Your tank is pressurized, and sometimes the pressure releif valve in the gas cap wears out.

DW

maxnewbie

Will do. However, would this be the cause of a rough or low idle?

dwapenyi

iTrader: (3)

It shouldn't affect idle. Maybe your throttle body needs a cleaning.

DW

NISMO808

iTrader: (2)

I've been getting the notorious EVAP error code too. I also noticed that when I open my gas cap I don't hear the hissing noise that I normally do from opening something that is pressurized.

njmaxseltd

iTrader: (19)

NISMO and Maxnewbie - The gas cap is cheap and could very well fix your problem. Unless you want to check or replace the purge valve, canister and all the hoses first. I know thats not the route I'd take. The manuals aren't perfect.

NISMO808

iTrader: (2)

do you recommend a genuine nissan cap or will the ones from trak auto suffice?

maxnewbie

Advice taken. Will go out today and buy a new gas cap and rerun the codes. Thanks!

bill99gxe

iTrader: (1)

Diagnostic Trouble Code 0705 points to a problem with the Evaporative Emission Control System.

This malfunction is detected when the EVAP control system has a leak or the EVAP control system does not
operate properly. (EVAP = EVAPorative emissions.) Possible causes include...

- incorrect fuel tank vacuum relief valve
- incorrect fuel filler cap
- fuel filler cap vent remains open or fails to close
- foreign matter caught in fuel filler cap
- a leak in the line between the intake manifold and the EVAP Canister Vacuum Control Valve
- foreign matter caught in the EVAP CVCV
- leaks in the EVAP canister or fuel tank
- leaks in the EVAP purge line (pipe and rubber tube)
- EVAP purge line rubber tube bent
- blocked or bent rubber tube to EVAP control system pressure sensor
- loose or disconnected rubber tube
- EVAP CVCV and circuit
- EVAP Canister Purge Volume Control Solenoid Valve and circuit
- absolute pressure sensor
- tank fuel temperature sensor
- MAP/BARO switch solenoid valve and circuit
- blocked or bent rubber tube to MAP/BARO switch solenoid valve
- O-ring of EVAP CVCV is missing or damaged
- water separator
- EVAP canister saturated with water
- EVAP control system pressure sensor
- refueling EVAP vapor cut valve
- ORVR system leaks

This is a "jackpot" code. It points to so many possible causes as to be almost useless. It may be accompanied by another DTC which is more specific.

bill99gxe

iTrader: (1)

Diagnostic Trouble Code 0304 points to a problem with the Knock Sensor.

The KS is attached to the cylinder block. It senses engine knocking using a piezoelectric element. A knocking vibration from the cylinder block is senses as vibrational pressure. This pressure is converted into a voltage signal and sent to the Engine Control Module (The computer).

This malfunction is detected when an excessively high or low voltage from the KS is entered to the ECM. Possible causes include...

- the harness or connector (The KS circuit is open or shorted).
- the KS


The KS may be checked with an ohmmeter.

1) Raise the hood. View the engine from the driver's fender. Look into the deep valley between the cylinder banks and below the intake manifold. Identify the KS as a black item fastened to the block by a single vertical bolt. A wire harness wrapped in black leads toward you, out of the valley. That is the KS sub-harness.

2) Follow the KS sub-harness to it's nearest connector. This is connector F121. It is located near the upper right-hand corner of the valve cover of the forward cylinder bank, as viewed from the front of the car.

3) Disconnect F121. You have to do a "press the latch and wiggle and pull" to disconnect it. F121 has only two pins; if you see more than two pins, you have the wrong connector. Use a digital ohmmeter capable of measuring more than 10 Megohms. You want to measure the pins of F121, not the sockets of the matching connector. Measure the resistance between a good ground (such as the battery negative terminal) and pin #2 of connector F121. On my car this is the highest of the two pins, the one closest to the front of the car. The factory spec is 500 - 620 Kohms.

The manual says you have to remove the intake manifold to replace the KS. However, I think that a person with good dexterity and a 10mm ratcheting box wrench could replace the KS without disturbing the manifold.

bill99gxe

iTrader: (1)

Diagnostic Trouble Code 0504 points to a problem with the Automatic Transmission Communications line. Pulse signals are exchanged between the Engine Control Module and the Transmission Control Module to assure smooth shifting during hard acceleration or deceleration.

This malfunction is detected when the ECM continuously receives an incorrect voltage from the TCM.

Possible causes include...

- Harness or connectors (The communications line circuit between the ECM and the TCM is open or shorted.)
- TCM
- Discharged or faulty battery

bill99gxe

iTrader: (1)

A gas cap ain't gonna fix what's wrong. I would suggest re-setting the ECU and then reporting the codes that come back when the light comes on again. Should that occur, then start by checking your knock sensor as prescribed above. Should that not work, then re-set your ECU again, wait for the lights to come on, then call the dealer and act completely ignorant about anything going on. Don't admit to doing a single thing except telling them the idle is low/rough and your check engine light came on.

However, if you're out of the basic warranty then we'll try to help further.

Albertt

Bill's information is just what you need to resolve your issue.

Also, I'm thinking that the OE filler caps are manufactured by Stant. Even if they are not, a Stant would be a perfect OE replacement. They are available at more chain auto parts stores.

maxnewbie

I wasn't getting a "Check Engine" light when I decided to run the codes. Just thought that the idle was running a little rough and RPM's at 500. I have the idle kicked up a bit to compensate for the low idle (currently running at 600 RPM). I was concerned with the error codes though.

bill99gxe

iTrader: (1)

The light wasn't on when you pulled the codes?!?


If so, then reset the ECU and see if the light does come one. Regardless, pull the codes again in a week to see what you have.


You have reason to be concerned. Something is wrong. I searched your profile and it looks like you've been having driveability problems related to your idle. It appears to be vacuum/evap system related, but it's still too early to jump to conclusions.....

maxnewbie

Replaced gas cap and now the only code I get is the 0304 knock sensor. I reset the ECU and still get the code. I guess the knock sensor needs to be replaced.

njmaxseltd

iTrader: (19)

I think you got of lucky with my "guess" on the gas cap. Bill gave an excellent write up on the EVAP code. It sure is a jack pot. Replace your KS and hopefully things will be fine. You may want to search for a thread where a guy actually fixed his KS by cleaning the ground from it. You can also check it with an ohm meter. I think they measure about 750 ohms??? Not sure on that figure so don't quote me there.

maxwillden

What year Maxima do you own? I had the same problem with my 96 Maxima, and it turned out to be bad emissions system components. It was however covered under a voluntary recall for 96 Maxima's... Even the knock sesnor code went away after the repair... Don't know how the two were ever connected.

$300+ Dollars worth of work covered by Nissan. It did not, however cover California Maxima's...

Good Luck...

(By the way, my first attempt was to replace the gas cap as well, as advised by my mechanic... It was only a temporary fix though. ECU codes came on again shortly after replacement of gas cap...)

dwapenyi

iTrader: (3)

I had emissions related check engine codes as well a while back. It wasn't covered by a TSB. Rather, every US car has a Federal warranty that overs emissions related components for 3 years/50K miles. I think for newer cars this has gone up to 8 years/100,000 miles. Not certain though.

The federal warranty took care of mine

DW