Hey y'all,

I've been searching for an hour, can't find specific info, and I'm running out of time. I'm working on my wife's 03 Navigator while she's out of town and need to finish it by Monday when she gets back! What started as a tune up turned into a fiasco- I had a coil pack code and some O2 sensor codes so I went to change the coil pack and found that someone (I suspect the dealer I bought it from) had cross threaded one of the spark plugs and ended up only grabbing a thread and a half. The plug blew out of the head and obliterated the coil pack so I fixed all of that and put it back together. The threads in the head weren't damaged so it ended up not being as bad as it could have been. Anyway, fired it up and drove it around and it ran much better, no surprise there. However, now the old codes have gone away (I did not clear them, they worked out on their own) but the CEL came back on and I have P0403 set and P0153 pending. I can't help but think the EGR code was caused by the truck running with an open cylinder somehow but I'm not sure where to begin with troubleshooting and fixing this. I cleared the P0403 code to test my theory and it came back before I even backed out of the driveway. Please help.

 

1. Which engine is in that '03 Navigator?

2. Which spark plug blew out?

3. For the P0403 check the resistance of the coil of the EGRVR. It should be between 25 & 40 ohms.

4. The P0153 pending indicates a slow response to the bank 2 forward oxygen sensor. Any exhaust leaks on bank 2 upstream of the fuel control O2 sensor?

 

Thanks for the reply. The plug that blew out was the third one back from the front on the driver's side; sorry but I can't remember the code number. The PCM threw the correct code for the plug/coil pack.

I couldn't wait for a response so I proceeded with troubleshooting techniques; I replaced the driver's side, pre-cat o2 sensor that had the pending code, reset the codes, and then proceeded to flush the radiator, which involves a lot of cycling the ignition and starting/stoping the motor. Finished all that (including holding the motor at 3k for a couple minutes at a time because I like to get the detergent swirling really hard before I drain it.) and took the nav for a test drive, romping the **** out of it for more than an hour. No CEL, no overheating, no rough idle. She seems to be fixed. I guess, if you're having only the P4303 code with no other exhaust gas rcirculation valve, the best bet is to replace the o2 sensor that's also throwing a code.

 

So you blew out the #7 plug which on bank 2. Only makes sense that this side (drivers) would throw a bank 2 lean condition with the plug removed.
Not sure if the condition would cleared itself with some more running time but pending codes will do that once self corrected.
Glad you are back on the road. I'm sure the wife too.

 

Alas since she is out of town until tomorrow she will never know the pressure he endured to please her. But then again, they never do!

 

Well, turns out that it still has an issue. I was driving it to a job site this morning as a final test run and the CEL came back on about halfway there (10 miles or so). My code reader was still sitting in the seat from this weekend so I hooked it up and got the damn P0403 code.

A little further backstory, I replaced the blown #7 plug and coil about a month ago. At that time I had codes set for both pre cat o2 sensors and several EGR codes. Since there was nothing else actually wrong with the rig I let her keep driving it all that time, assuming the codes would clear themselves out. When I went to work on it again this weekend I figured I'd probably have one bad o2 sensor so I was surprised to find that I had the pending o2 sensor code rather than a hard set code. Since I replaced that sensor I'm only getting the EGR code but it's frustrating the hell out of me because P0403 is basically a generic code saying that something somewhere is out of whack with the EGR system but gives no direction. This would be much easier to diagnose if I had two EGR codes thrown. I just don't have time to chase gremlins.

 

Did you check the infamous vacuum tee coming off the passenger side valve cover/ egr valve. It deteriates, causing a vacuum leak and misfire condition. Many posts here about that specific issue. Maybe an easy, non gremlin fix.

 

I checked what I thought was the vacuum T but, now that you ask, I'm not so sure I was checking the correct fitting. I've looked at several pictures of this elbow/T but none of the line routing looks like mine. I also sprayed starting fluid all over the place back there to check for a surge but got no response.

 

The P0403 code is pretty direction specific. It is indicating that the EGRVR circuit voltage is out of the expected range.
Since voltage is a function of current and resistance, that is why I suggested:
"For the P0403 check the resistance of the coil of the EGRVR. It should be between 25 & 40 ohms."

What resistance is your's showing?

And not to start a hijack, but just for my own education, did 2003 Navigators only get the DOHC engine, or was the Essex & Windsor 5.4s also installed in the Navigators that year?

In other words, what is the eight digit of your vin?

 

I missed that suggestion I hate to ask this and sound like a newb but, where is the solenoid located to check the resistance? Either myself or the nav are always on the road so it's difficult to spend much time with it. If you can point towards it ill try to check it tomorrow night.

To answer your other question, I'm fairly certain there was only one motor option for these rigs but I'll check the vin out tomorrow as well and report back.

 

Should be bolted to the driver's side of the upper intake manifold.