Occasional P0400 Code

[xxx]

you left the jumper in the DLC , timing freeze.
this makes the cat get very hot if driven like that.. see DLC in front of battery, remove you jumper.
i bet that smog test was not done with 1530s.....
no smog shop will run the the smog test with any CEL glowing. running.
so the sniff test is moot.
no lie. the NOX is bad. im sure.

but why is your closed loop failing at idle, let me guess, 1530s? nah... its old dead code. you do know it takes many driving cycles to erase many codes.
i never do that, i clear them when wrong or after a timing change.
remove the jumper, then reset ecu, and show
closed loop at idle
i like do fix the easy things, first
1530 is wrong, clear it.
then get closed loop to work at idle
my guess is LTFT at idle is off the map..... is it?
does the ECT show, 180F solid like a brick? driving or whatever?
ok its 185. but is it solid, not wavering... if during the last thermostat was installed
with no rubber ring.? causing it to float?
if it don't run right at idle , all bets are off
the scan too must show crosscounts like this link shows.
and closed loop, or the motor is gross lean. (lean causes NOX, so i bet lean)
your HC and CO are low but that is just the cat working..very good.
the NOX is thru the roof.
You can not tune the engine at the tail pipe the cat hides the truth.
but if you see high HC or CO or NOX, its 10x worse the motor.

see photo 5 and 6 (CL and 02 swings, hot idle) see LTFT ! minus 3.
A full OBD2 scan
see photo 7 when you race motor fast see that advance swing way out.. 42
that proves the 1530s are old data that swing out., clear old data and lets go forward.

all kicks go to closed loop, in 10second from cold start.
that happens due to the magic of the heated 02.
does that scangauge even show all DTCs even the 02 failures? (sorry not a SG2 guy)
P0135 is bad heater B1S1, we must not have any 13x codes.

if the 02 is railed at idle, we need to fix that first.
maybe you have an air leak? from MAF to intake valves?
the 16v is very hard motor to seal up. after many years.
the ecu can correct for tiny leaks, but not past

i can see an air leak causing lean from idle to 15mph sure.
but the scan too will show that.
via 02 plots and LTFT
a large leak will be +20% LTFT or more,,,, or railed. the ecu does set DTCs for railed 02
p0171 I forget the trip points on 171s

your motor is sick, lets fix that.
the EGR can not correct gross lean motors. its not for that. helps but will not win.

[Glas1700]

You were right. A couple of days ago I put the jumper in, set the timing, removed the jumper and took it for a drive. It ran well, no codes set. When I got back, I decided to do another quick timing check, put the jumper in and forgot to remove it after checking the timing. Fortunately, I didn't drive it with the jumper in, only idled it on the driveway until it warmed up. Got closed loop this time in about 15 seconds.

I've done a thorough check for air leaks, especially from the air cleaner to the plenum and everything is well sealed there. Could be a leak between the plenum and intake manifold or the head, will check. Coolant temp is solid after warmup, so I think the thermostat and seal is okay.

Still raining here in the SF bay area, so other checks will probably have to wait for a couple of days. Most of my experience is pre-emissions with carbureted Chevy engines, not much with OBDII, it's a learning experience.

[xxx]

no scan data, means we work blind.
that idle, not holding closed loop, is the key, im sure. SGII= "CLSD LP" HOT.
it must do that.
even a carb car will fail , with a base gasket leak. goes lean.
yes, that jump turns the engine in to a giant lawnmower engine. w/ no advance.
have you sprayed, the MAF with crc maf spray yet? no touch, just from 6inchs.?
they can coke up, and cause lean then add a leak and it gets worse.
THE SG-II
is not a full scan tool, its primary purpose is to show, mpg.
it has like 8 PID display out of 100s. very limited.
i just read the 28 page users manual. and it cant do LTFT nor do 02 graphs.

a better tool is the Palmer. far better, or even the Android app. from them.
or a hand held Autel MS509 or rent a real tool from any auto store.
no better bang for buck this

Amazon.com: Autel MaxiScan MS509 OBD-II/EOBD Scanner: Automotive

Amazon.com: Autel MaxiScan MS509 OBD-II/EOBD Scanner: Automotive

here is mine at idle plotting 02, in closed loop




also keep and open mind, some times it 2 problems,
make sure the #4 exhaust tube (port to collector is not cracked) many are.

[xxx]

ill post this about the 16v induction system. Im not saying this is it, only what if it is stuck lean at idle.
i have this pure air page.
the end shows the vast numbers of possible leaks.

http://www.fixkick.com/IDLE-AIR/pure-leaks.html

they (leaks) can each add up. until the 02 is overwhelmed.
keep in mind as you tip in the throttle, the ecu goes to enrich mode, and closed loop drops.
if there are leaks, now you get lean, at low throttle openings. like gently leaving a stop sign. it bogs...or hesitates.

if you have a 3sp, A/T tranny there is one more, leaker, the VAC modulator port and hose, end to end.
in a shop they would use a smoke machine and find these all effortlessly.

[Glas1700]

[QUOTE=xxx;352678]
THE SG-II
is not a full scan tool, its primary purpose is to show, mpg.
it has like 8 PID display out of 100s. very limited.
i just read the 28 page users manual. and it cant do LTFT nor do 02 graphs.

a better tool is the Palmer. far better, or even the Android app. from them.
or a hand held Autel MS509 or rent a real tool from any auto store.
no better bang for buck this

Amazon.com: Autel MaxiScan MS509 OBD-II/EOBD Scanner: Automotive

Amazon.com: Autel MaxiScan MS509 OBD-II/EOBD Scanner: Automotive

Thanks for the continued help, I really appreciate it.

The system does go into closed loop almost immediately, now that the jumper is removed.

My SGII will do LTFT using what is called the XGauge function, so I programmed it and LTFT varies between 0 & 1. I decided to order a cheap ELM 327 adapter to try out the Android apps. The Autel tool looks interesting, but has many bad amazon reviews, mainly about lack of customer service.

I normally use the SGII in my MB diesel powered motorhome to display BST (turbo boost), FWT (Fahrenheit water temp), IAT (intake air temp) and LOD (% engine load). I calculate MPG the old fashioned way, miles driven divided by gallons used.

[xxx]

yes there is no customer service but why would you need that?
it works, perfect so just use it. it's like a hammer.... and does graphs too.

did you run the smog test with the jumper in too>? way bad that
lawn mower mode makes big black smoke.
i think not,
it's just a bad EGR System. you LTft IS OK.
Be careful of LTFT, there are like up to16 slots for that .
you want slots for hot only, 180F, and idle and at failed, smog load.
CL at idle, great. news.
so that means no leaks, and EGR is the fail. (CL good and LTFT low "centered")
find a way to get the full EGR flow from the #4 exh port all the way to HOLE#1
Hole 1 is behind the TB base, all EGR flow, there in a mono port.
it must be 11mm in diameter, not 5.
sorry im no SGII person. and didn't knowthere are extentsions the code.
great !
cheers !