Hi all,

the engine shakes, I'm getting the following codes:
P0037 - HO2S Heater Control Circuit Low (Bank 1 Sensor 2)
P1316 - basically says "too much misfire"
P0300 - random misfire

also noticed that the Bank 1 Sensor 2 output voltage stays flat.
Fuel trims: after starting the car they vary, then I think it gives up and they all stay at zero exactly.

Few questions:
1) I'm I correct to think the problem is that because Bank 1 Sensor 2 gives nonsense the fuel trims stay at zero and therefore the engine runs rough at idle?
2) I thought Bank 1 Sensor 2 (downstream) doesn't affect the fuel trims, just checks the cats are working?
3) OK, so the car is confused, sets the fuel trims to zero. In ideal case the engine should run OK. The fact that it shakes means there is vacuum leak?

many thanks in advance for your help.

 

I fought a similar problem last week with my '01 XKR spitting a p1646 code. There's some squirly stuff going on with the XKR O2 sensor diagnostics on these cars...

The reference books say that on mine (as yours) P1646 is a secondary fuel pump relay failure, but replacing the Upstream O2 sensor on bank 1 with a proper Denso unit fixed the problem.

The other symptom I had was the engine running in open loop mode which made me suspect the O2 sensor rather than the secondary fuel pump plus some misfires.

If I had to guess (which I am) and jumping to a solution rather than detailed diagnosis... what I think may have happened is:

You've developed a misfire which has stuffed your probably old and quite tired B1S2 sensor through an excess of O2 or other contaminates flowing through the exhaust.

The ECU has seen the stuffed sensor heater when you turn the ignition on and it try's to warm the sensor up, had a hissy fit, and decided that if it can't measure O2 and fuel trims properly, then it's just going to sit in the corner and sulk... and then put both banks into open loop mode using a default trim table. Why it shuts off adaptive fuelling on both banks when just one sensor is out I don't know... but it does. Check your obd fuel system status flag for whether you're in open or closed loop. Having said that, since the engine takes a few minutes before it goes closed loop anyway, you could be doing damage running it that long to warm it up, so maybe focus on the misfire as a priority.

You can also check the continuity of the heater element on the O2 sensor by disconnecting the (black I think) plug at the firewall for sensor B2S2 and check continuity on the heater wires. You can also check for a short to ground on the heater control wires... the table I've got says pin EM84 -07. It'll be documented here somewhere how to do that... I had the sensor heater failed (open circuit) so I just swapped out the sensor.

You've still got a random misfire but not bad enough to trigger any misfire codes (yet) but you can't use the trim readings to narrow down the bank... That random misfire could be a misfire on multiple cylinders, or just on one occaisionally, but it's not bad enough yet for the ecu to lock it down to a specific cylinder.

FYI... My misfire started like yours as a p0300, then developed to a p1316, and then a p1314 (pending cat damage) and I freaked... turned out to be on just Cylinder 7 (after a few restarts it threw a p0307 code)... which is just below the oil filler cap, and right where any coolant overflow from the expansion tank will make its way if there is a leak in the B2 coil cover gasket. When I pulled the coil over C7 there was both oil and water in there, but only in that cylinder... Wasn't me did it... honest... well, maybe the coolant was down to me!

I swapped the coil packs from 5 and 7, cleaned out the plug hole, squirted some contact cleaner in and the misfire went away.

A large vacuum leak is likely to affect multiple cylinders, or all of them, which you don't know yet. but if it's large enough to cause misfires, squirting some carb cleaner around the intake lines and intercooler inlet should find it pretty quickly.

You might have a low fuel pressure issue if all 8 banks are randomly misfiring - bad or dying pump, blocked filter, bad pressure return valve, clogged injectors... it's well documented on here how to diagnose them.

You might have a bad injector(s) which is a PITA since thats an intercoolers off job to replace/troubleshoot them so that's the last thing you want to have to diagnose.

I don't think that changing the O2 sensors out will stop the misfires although that one sensor is probably toast, and when you do change it out, get a proper denso, I've heard that they're more reliable than the universal cheapo ones..

Find and fix the misfire first and then deal with the sensor afterwards.

Someone will jump in and advise you to check your upper timing chain tensioners (which it could be if she's running really rough but remember that all the cylinders on one bank would be affected then). I'm not sure that she'd even fire up!?

It's either air, fuel, spark or compression, so i'd start with checking for vacuum leaks with carb cleaner and fix any you find, then check the fuel rail pressure, and then start checking coils and plugs. If you're 'lucky', whilst you're doing that, she'll throw a more targeted misfire code for you.

Having said all that... I'm certainly no expert... and to prove it, I spent 30 minutes last sunday with an open ended 22mm spanner undoing my B1S1 sensor, 1/8 of a turn at a time, only to have it retighten itself after each turn as soon as I lifted the spanner off to reposition it... 30 Gorramn minutes before I realised that I hadn't snipped the tie wrap holding the sensor away from the manifold, so as I undid the nut, it tensioned the cable, which then promptly untensioned itself when I lifted the spanner away by doing the nut back up.

THIRTY MINUTES!!! (Shameful look)

Good luck.. and snip the tie wraps!

Jack.

 

All you need to do is loose a slipper on the secondary tensioner on one side and you can easily jump a tooth on the cam sprocket and she would run idle very rough and most certainly fire up. If the tensioners have never been upgraded this is a well advised check.

 

Apparently you're using the wrong books or misreading. The Jaguar one for the car is clear that it relates to an O2 sensor...

 

Could be you have a clogged egr valve, or the bypass valve for the supercharger is faulty (leaking vacuum) or both. They can cause the car to run rough, and kill your o2 sensors.

 

At the end it was way more serious. Cylinder #5, exhaust valve seat had came out.

Changed the whole cylinder head from a spare engine I have. Will try to fix the cylinder head I took out, to have a spare.

thanks for the help. A.

 

You didn't mention that the engine overheated. That along with the misfire would've been a clue where to go.

 

I'm not aware of the engine overheating. I never got a warning light or anything ...

 

Check your coolant level...if it is too low, the fluid would be below the temperature sensor, and you can overheat and never trigger the temperature gauge or the overheat warning light.

On these cars, a dropped valve seat is often the result of overheating.