2005 Frontier codes - P0420, then P0507, now P0302

Joined
Oct 27, 2021
Messages
7
Hey everybody, long time lurker, first time poster. Have a 2005 Nissan Frontier 2.5L with 5spd manual, 180k miles. Been a great truck overall. I will admit to stupidly allowing engine oil level to get very low earlier this year, this has been my only sin. Restored oil to 5qts upon discovery. I now understand the truck burns about 1 qt/4k. I don't think the current difficulties relate to that episode, but who knows.

I have already independently research all of the following codes. I also am referring to a set of Nissan maintenance manuals I have for the truck. I'm not an experienced mechanic (have a little experience, e.g. pulling intake manifold & replacing sparks, etc.) but I would like to solve this issue.

This summer, it began throwing P0420 (bank 2 catalytic). I don't live in a state with emissions, so I decided to take the wait and see approach. Code only came in every 2-3 weeks, actually didn't come in much recently at all.

On Sunday, I was doing some steady-state driving in the mountains. I noted what seemed to be a bit of misfiring - pretty minor but noticeable. After I got back into stop and go driving, I started getting some serious stuttering during acceleration. Got home and code was P0507, high idle. Scratched my head.

Stuttering continued this week. Idle is either irregular or high. What I have noticed is the issue gets progressively worse as the truck warms up (suggesting possible vacuum leak thru hose as it heats up & expands, etc.).

Today, I finally got a P0302 code (cylinder 2 misfire). Woohoo!

Here's what I've tried so far:

Monday - pulled intake box so I could access spark plugs to replace them. Plugs were 100k worn (double platinum NGKs) but not abnormal. Torqued new plugs to spec with torque wrench. Reinstalled intake box with new gaskets and torqued to spec.
Tuesday - cleaned MAF sensor with proper CRC cleaner, no effect. searched for vacuum leak with starter fluid, no luck
Wednesday - During spark plug job when I pulled the intake box, I "found" the PCV valve was literally sheared off above where you would put the socket on it. The nipple side was still in the vacuum hose, and the PCV valve spring and "bullet" were laying in the threaded portion. The two sheared parts of the PCV valve body were held together by vacuum hose tension. I didn't know what the PCV valve was at that time, but I quickly learned that needed to be addressed. Replaced that Wednesday but no effect. Maybe the truck won't burn oil any more though. I still don't understand how this didn't fix the P0507 code.
Today - searched for vacuum leak with water sprayer, no luck

Over the last few days, I've done the idle air relearn process several times, with no effect.

Here's what I'm thinking about trying, in rough order:
1. Keep looking for vacuum leaks. Maybe I'll try using a straw or something this time.
2. Take air tube off throttle body and inspect for carbon buildup, clean with throttle body cleaner as necessary. Probably also inspect and reseat electrical, then redo idle air learn procedure. Try to figure out where the idle air control valve assembly is in the throttle body.
3. Considering swapping coil packs on #2 and say #3 cylinders, see if the P0302 swaps to a P0303. This will be a huge PITA as I will have to pull the air box again, all the bolts/nuts are blind and it's tough as hell to put a wrench on them. Also I don't have additional gaskets for the air box, I'm not sure if I need to but Nissan says replace each time. But this issue started with P0507 so I'm thinking it's probably intake/vacuum related.
4. Go down the P0302 rabbit hole.

If you were in the same bind, would you proceed as above, or would you go down a different path?

Thank you for your thoughts!
 
Joined
Feb 25, 2019
Messages
1,807
Location
Texas
Yeah i'd've tried swapping coils before changing plugs first thing because if that doesn't fix it you're looking into possible wiring harness issues.

As for the vacuum leak you couldn't immediately hear any hissing noise? Have someone start it up and be there to listen.

Also hopefully the pcv valve fixes the consumption and i wouldn't worry about the cat. To be honest if i didn't need emissions i'd've already chopped them all off my vehicles and sold them myself.

Do you have any kind of basic scanner than can measure things like fuel trim and pressure. a cheap generic elm 327 is usually good enough to see those values. anything pressure or flow related can usually be checked.
 
Last edited:
Joined
Jul 20, 2020
Messages
74
Location
Omaha Ne.
The lean condition could be causing the misfire. The high idle does suggest unmetered air in the engine. The mass airflow sensor would be suspect if I were looking.
 

sippyCUP

Thread starter
Joined
Oct 27, 2021
Messages
7
Yeah i'd've tried swapping coils before changing plugs first thing because if that doesn't fix it you're looking into possible wiring harness issues.

As for the vacuum leak you couldn't immediately hear any hissing noise? Have someone start it up and be there to listen.

Also hopefully the pcv valve fixes the consumption and i wouldn't worry about the cat. To be honest if i didn't need emissions i'd've already chopped them all off my vehicles and sold them myself.

Do you have any kind of basic scanner than can measure things like fuel trim and pressure. a cheap generic elm 327 is usually good enough to see those values. anything pressure or flow related can usually be checked.
So I have a ThinkOBD 100 and I'm learning right now how to read the live data so I can figure out the fuel trim situation. It seems like I can hear a hissing noise but it's tough, I need to work more on that.
 
Joined
Feb 25, 2019
Messages
1,807
Location
Texas
So I have a ThinkOBD 100 and I'm learning right now how to read the live data so I can figure out the fuel trim situation. It seems like I can hear a hissing noise but it's tough, I need to work more on that.
Better to hear a hiss than not since it would be a bigger issue. And yeah you'll learn quick with live data and like Matt said it could be the intake gaskets causing the idle and vacuum. Can't believe I forgot to think of that sooner I had that same issue in my 2000 ranger way long ago.
 
Last edited:
Joined
Jan 2, 2004
Messages
9,314
Location
California
Nissan QR25DE with the all-in-one intake/air box? I replaced spark plugs on one, I made it a point to replace all the seals for the manifold version. It’s also really easy to miss connecting the brake booster vacuum line as well - but that would be obvious.

Did you use an torque wrench to tighten the nuts and bolts? I had a feeling these things crack easy when I took it off.
 

sippyCUP

Thread starter
Joined
Oct 27, 2021
Messages
7
Yes it is a QR25DE engine. I replaced the seals and then watched them as I snugged up the box on the two studs is mounts to (man that was not fun), so I am reasonably sure the gaskets all stayed in their spots, but yes, something I could check on. Also yes, I did use a torque wrench to the Nissan spec.

OK, so I spent an hour learning fuel trim, then went for a nice drive. Open loop on startup, no issues. Closed loop, the acceleration stuttering starts. Surprisingly I couldn't get it to behave too rudely under acceleration, still doing it some though.

Open loop and cold, idle isn't too bad, mild to moderate stuttering. However, when fully warmed up and closed loop, the idle oscillates between 1500 and 1000 RPMs... say 2-3 seconds at 1k, then like 5-6s at 1.5k, then back to 1k for 2-3 seconds....

Here's what I saw on trims and O2:

LTFT: Started at 0 (BTW I left the negative terminal off last night), then crept up to 0.8%. My thoughts - wasn't expecting this, looks good.
STFT: Mostly around 0-3, didn't bounce around much at all.

So trims looked really good, both at idle and driving.

O2 sensor 1: OK, this was wack. It was basically at 0.350 all night. I know understand that the ECU should be bouncing between slight-rice and slight-lean states on a sin wave, which would be reflected by the first O2 sensor bouncing between 0.1 and 1.0 volts. The reading moved around a ltitle bit, but it stayed stationary, it didn't change second by second. Seems very suspect, bad sensor or wiring? Or ECU issue? Maybe the truck stayed in open loop the whole time and didn't oscillate the richness? Need to learn more.

O2 sensor 2: stayed around 0.750 the whole time. This seems about right.

More questions but also seem to be narrowing things down.

EDIT: I watched the O2 sensors while driving in about July when P0420 first came up. Sensor 1 was bouncing around at that point. So either the sensor or wiring is bad, or the ECU isn't oscillating the air/fuel mix.
 
Last edited:
Joined
Dec 8, 2011
Messages
895
Location
MO, USA
Very few vehicles stay at Stoichametric fuel trim ! The rich/lean cycle lows the 3 bed catalyst to heat up faster and clean the exhaust
 
Joined
Dec 19, 2013
Messages
6,702
Location
Fort Worth, Texas
Nissan introduced Electronic Throttle Control in 2002. The engine control module (ECM) controls the position of the throttle plate with a throttle motor built into the throttle body. There are two throttle position sensor inputs to the ECM from the throttle body along with two accelerator pedal position sensor inputs from sensors located at the accelerator pedal.

A common problem with this vehicle is a high, and sometimes surging, idle speed – especially after the throttle body has been cleaned. This typically results in a code P0507 to be set as engine speed of 200 RPM or more over the target idle speed will set this code. The throttle plate develops carbon buildup over time, restricting air flow into the engine resulting in the ECM opening the throttle plate more to compensate for the restriction of air.

When the throttle plate is cleaned, more air is allowed to pass the throttle plate resulting in the high idle speed. The common repair is to relearn the idle. The Nissan Consult II factory scan tool will relearn the idle speed but the scan tool is not available in most aftermarket repair shops so Nissan provided a manual way to relearn the idle as well. This manual procedure works most of the time but there are some vehicles that end up returning to the dealer for the factory scan tool to relearn the idle when the manual procedure fails.

To perform the manual relearn procedure:
1. First the technician must perform the accelerator pedal released position learning. This procedure begins by making sure the accelerator pedal is fully released. Then turn the key ON and wait at least two seconds. Turn the key OFF and wait at least 10 seconds. Turn the key ON and wait at least two seconds and then turn the key OFF and wait at least 10 seconds.

2. Perform the throttle valve closed position learning. This is a very simple procedure that once again involves making sure the accelerator pedal is fully released and then turning the key ON, turning the key back OFF and waiting at least 10 seconds. Listen for the operating sound of the throttle motor during this procedure to verify that the throttle plate moves.

3. The last part of the relearn procedure is idle air volume learning. Idle air volume learning begins with the preparation steps to make sure the system is ready to relearn. The preparation steps include making sure the charging system is working normally – battery voltage above 12.9 volts at idle, the engine should be fully warmed up, the transmission should be in Park or Neutral – the Park/Neutral position switch indication on the scan tool should be ON. All electrical loads should be OFF, the steering wheel should be straight ahead and the vehicle should be stopped. The transmission needs to be warmed up as well. On automatic transmission vehicles, the transmission fluid temperature sensor needs to read less than 0.9 volts. Drive the vehicle 10 to 15 minutes to properly warm up the engine and transmission.

4. After the preparation steps have been completed, begin with the idle air volume learning procedure. If the engine idle speed is excessively high, turn the engine off and disconnect two fuel injectors at this time to bring the RPM down. Nissan TSB# NTB05-067 addresses the P0507 code and disabling fuel injectors to bring the engine RPM down as the idle will not relearn if the engine RPM is too high.

5. For the remaining steps in the relearn procedure, it is necessary to have a watch or clock with a second hand or a stopwatch. The times indicated will need to be followed as exact as possible. Read through the remaining procedure prior to performing it to know what the steps are so they can be performed in the correct time given.

6. Verify that the accelerator pedal is fully released, turn the key ON and wait exactly 3 seconds. Then fully depress the accelerator pedal and then fully release the accelerator pedal quickly five times within 5 seconds.

7. Wait exactly 7 seconds and then fully depress the accelerator pedal and keep it depressed and after about 10 seconds or so the Malfunction Indicator Light (MIL) should start blinking. If the MIL does NOT start blinking after waiting 20 seconds, turn the key OFF and wait at least 10 seconds and repeat the procedure beginning with verifying the throttle is fully released and turning the key ON and waiting exactly 3 seconds and then fully depressing the accelerator pedal and then fully releasing the accelerator pedal quickly five times within 5 seconds and continuing on from there. Repeat the procedure as often as necessary until the MIL starts blinking.

8. Once the MIL starts blinking, let it continue to blink until it stops blinking and comes ON steady (usually about 10 seconds after if starts blinking). When the MIL stops blinking and comes on steady, release the accelerator pedal within 3 seconds of the MIL coming on steady and then start the engine and let it idle. The learning procedure begins when the engine is started so the previous steps were just to get the system into the learn mode.

9. Let the engine idle for about 20 seconds. If the relearn was successful you will notice a dramatic RPM drop during this time. Then turn the engine off and reconnect any fuel injectors that were disconnected and restart the engine and verify the idle speed has returned to normal.
 
Joined
Aug 23, 2010
Messages
3,635
Location
pa
great info from a pro!! Cline often takes the time for for posting great correct professional procedures, a great guy for sure!! my 38 thou preowned 11 SV fronty V-6 throws cat codes in very cold weather BUT they go away! reading + my friends experience shows cat issues as common! so many possible fixes when modern tech fails its lucky if you have a competent repair service in your area
 
Top