2001 Infiniti QX4 intermittent SES flashing

[MLW9110]

I’ve had the QX4 about a year. It was a gift from a friend. Has 204,000 miles. It has some annoying, hard to troubleshoot problems.
1. Starter not engaging. Most of the time turning the ignition to start works normally. Occasionally, nothing happens when turning the key to start except the start relay clicks. Usually it will start normally after I jiggle the ignition, gear shifter or curse at it. None of these actions are consistently reliable. Sometimes it will start immediately after a failed attempt. Sometimes it will take anywhere from seconds to minutes to work again. Hasn’t stranded me yet, it always starts eventually. The relay seems ok. Tapping on the starter while someone is holding the key to start has no effect. Engine cold, engine hot, no difference. I’d try replacing the starter but when it starts, it seems normal.

2. SES light on all the time. This appears to be a bad O2 sensor, bank 2 sensor 2. Code P0161

3. SES light flashing. Car will drive normally, then run rough and the SES light will flash. Sometimes will clear after revving engine in neutral while driving or flooring gas pedal to cause downshift. Sometimes it feels like it’s the transmission might be hunting between gears. Sometimes the flashing SES will stop after a few minutes while driving normally, sometimes it won’t clear until after the engine is shut down. Again, none of the things that seem to work to stop the flashing work consistently.

Codes stored. P1320, P0303, P1140.

I don’t have much money in the QX4. It’s my tow vehicle for infrequent motorcycle transports. I’m considering buying a 2001 Toyota Tacoma from a friend but hate to give up on the QX4. I’d be inclined to invest in repairs for the QX4 but because of the intermittent nature of the problems and the multiple components that are involved, I’m hesitant to take it to a shop. I can try to troubleshoot myself but I have other things I’d rather do!

Since I typically can fix my own stuff, I don’t have any experience with having a shop work on a SES problem with multiple possible solutions. I guess I’ve been lucky not to have had to deal with this kind of problem before. What are my chances of a shop fixing my QX4 at a cost less than its value?

Mike-Bremerton, WA

[VStar650CL]

The flashing MIL, P0303, and P1320 all point to a dying coil or plug on #3 cylinder (middle plug on the passenger side). The P1140 is for the cam position on the same bank, so you might just have a crappy engine ground causing both issues. Since the righthand bank is a PITA on axial VQ's, I'd start by replacing all the plugs and coils on that bank (or all around), then clear the codes and see what if anything returns.

If you can hear the starter relay click when you turn the key, then the ignition switch isn't causing that problem, the starter is. Either the brushes or the ring contactor are shot and intermittently failing to connect with the armature. Needs a starter. That isn't a terrible job, just awkward. Here's a pretty good vid:
https://www.youtube.com/watch?v=7LCgMH9cDdk

[MLW9110]

I decided I needed to attempt to fix the QX4 myself. It wasn't as hard as I anticipated to get to the coils on the right side. The only curse worthy part was when I got a spark plug socket stuck in the #3 well. Now I know that's not the right size socket!

Cleaned 2 engine grounds at top/front/left and 1 ground at right side middle.

Pulled #3 coil and spark plug. Gapped plug, it was about .005 too big. Plug had light brown deposit and was not wet.

Swapped #3 and #5 coils.

Cleared codes. Drove 20 miles. SES light did not come on. One brief period of engine stumble at idle. SES light came back on after getting home and cycling engine on. P1320, P0161 and P1140 stored again. Engine was running smooth at idle.

I'll drive the car a while and see if the misfire follows the coil.

[VStar650CL]

The P1320 means at least one of the coils or plugs isn't firing cleanly. It's a feedback code and there's really nothing else which causes it. In fact, it often results from using crap aftermarket coils, although that probably isn't the case here. With 204K, they're probably just getting long in the tooth. My advice is just change them (and stick to the riceburner brands, Denso/Hanshin, NGK/NTK, Hitachi, etc).

P1140 is just a bad sensor about 95% of the time. Check for 12V at the Black/White wire and backprobe the Black wire for a voltage drop test. If there's more than 50mV from Black to the battery negative post with the engine running then your grounds have an issue. Check again from the engine block to the post, if that's also above 50mV then your main ground cable is crap. If that all checks out, replace the bank1 cam sensor. Same deal, stick with riceburner brands.

[MLW9110]

Replaced starter. Wasn't that hard.

Removed Bank 2, #2 O2 sensor. New one on the way. I'm going to wait until I get the new sensor in before I do anything else.

[MLW9110]

New starter working good.
O2 sensor installed yesterday. Works good.
Code P1140 still coming up. Code is for intake valve timing control position sensor, right, bank 1. Right side sensor was 0 ohms across two of the pins. Swapped with left side sensor. P1145 came up so problem followed sensor. New sensor on order from NAPA.

Cylinder 3 misfire has not reoccurred or moved to cylinder 5 but I've only driven the car about 25 miles.

[VStar650CL]

Sounds like you're getting a good handle on it bit by bit.

[MLW9110]

New sensor fixed the P1140/P1145 codes. The misfire has not reoccurred. Starter is working good.

Got the oil changed, filled the gas tank. SES light has stayed off and there are no pending codes stored.

Glad I decided to not be lazy and attempt repairs myself. I tend to overthink things. This time the codes stored led directly to the cause of the SES light and the intermittent starter problem was the starter and not some other gremlin causing mischief.

VStar650CL, Thanks for your guidance!

[VStar650CL]