Code 43 "Electronic Spark Control (ESC) Circuit - Knock Sensor

[Qavion]

I hadn't used my Esprit SE for a few months, so I thought I'd run the engine for a few minutes to make sure all was ok. After 10 minutes, probably well after the engine management system went into closed loop mode, the engine started to get a bit lumpier than usual and shortly afterwards, the CEL came on.

My laptop needed recharging and it wasn't until the next day I could run Freescan. I couldn't get the CEL to re-illuminate, but I noticed a fault in Freescan : "Code 43 "Electronic Spark Control (ESC) Circuit - Knock Sensor".

The knock count seemed to remain at 12 no matter what the engine rpms were (car not moving, so no load). The Freescan manual seems to suggest "0" or a few counts is acceptible for idle.

The engine is still lumpy and seems to miss a beat from time to time.

Should I replace the knock sensor or could a simple high resistance on the electrical connector cause this problem? I'm also thinking about changing the ignition module and coil packs for the lumpiness problem.

Thanks

Cheers

Ian.

Edited May 6, 2016 by Qavion
Addit info

[Bibs]

It could be knocking due to old fuel, get some fresh petrol in there

[Peteric]

Dont know about the cel however if you start the engine or cut the engine off with freescan running it certainly causes a knock count of about 12 on mine. Make sure its not counting knocks when starting or shutting off as i understand this is completely normal.

[Qavion]

Quote

It could be knocking due to old fuel, get some fresh petrol in there

Could be. I put a can of Liquid Moly Carb and Valve Cleaner in the tanks shortly before the first engine run. I'm sure I read somewhere that it helps with less-than-fresh fuel, but now I'm starting to think I was led astray.

Quote

Dont know about the cel however if you start the engine or cut the engine off with freescan running it certainly causes a knock count of about 12 on mine. Make sure its not counting knocks when starting or shutting off as i understand this is completely normal.

Ah, this was a constant 12. I assume Freescan just doesn't record the highest valve.

Anyway, I'll take the car for a run, but not too far from home. I hate driving with the CEL illuminated, not knowing what the reason is.

I'm wondering how the knock sensor reacts to knocks. Does it change resistance (causing a voltage change in the circuit) momentarily or does it operate on some kind of piezoelectric principle?  I'm just wondering how it reacts to high connector resistances.

Thanks, gents.

Cheers

Ian.

[Barrykearley]

looks simple to check out.

you need "real" new petrol in there - modern stuff goes stale and horrible really fast.

[Qavion]

Good info, Barry. Thanks.

It's probably not an AC signal in the truest sense, but a modulated DC signal. The sensor generates a higher resistance (during knock) and pulls down the voltage. 

I'm still not sure what the 12 represents:

12 knocks of a specific amplitude in a 3.9 second interval?

12 is measured on a scale based on amplitude x frequency?

Anyway, I tried to reset the Code 43 as per the instructions, but my laptop mouse and trackball stopped working (I have an ancient laptop running Windows 95 with a serial port suited to Freescan). I've just got that fixed, so I'll have another go later this week.

Hopefully the solution to this is simply to drive the car more (so that the fuel is refreshed regularly).

Cheers

Ian.

 

(EDIT: The text reads "If ECM terminal "J1A11" is above 3.75 volts indicating an open circuit, Code 43 will be set". This seems to suggest a disconnected sensor, or perhaps even a very high resistance may cause the code. I'll definitely check the connector on the sensor.)

Edited May 7, 2016 by Qavion

[Barrykearley]

You need a copy of the freescan manual

the knock sensor is counting the amount of detonations. These are bad detonations not good ones ie  pinking. Old fuel can cause that for sure if it's running rough. Unfortunately it could be wiring, sensor or ecu issues - all of which are easy to check for with the flow chart.

first off - I'd be wasting that fuel and getting some fresh - that could well solve the issue

[Vulcan Grey]

as long as the knock counts aren't increasing, then it is usually just a little transient issue upon startup.  Not a problem, and pretty common on the Esprit.

 

If the counts are increasing, then that's a problem. 

The sensor wire is easy to knock loose... during an oil change or other work.

The knock sensor must also not be torqued in too tight, or too loose.  I think the spec is 14 ft-lbs. 

[Qavion]

Quote

the knock sensor is counting the amount of detonations.

There must be some kind of time frame for this, though, otherwise the count would just get bigger and bigger. I do have the Freescan manual, but it doesn't specifically say this. Also, I wasn't sure if detonation was black and white. Are there degrees of severity? Going back to my aviation days, on modern jet aircraft there are accelerometers on the engine casings which generate vibration readings in the cockpit. There is a graphic scale displayed continuously, but if the vibration reaches a certain amplitude, an alert is generated. The number of vibrations over time is not recorded (but is used in other ways).

I'm wondering if I should drain the fuel at the crossover pipe (between the tanks). Do the rubber hoses come off easily or do they (typically) fall to bits? Perhaps I could just siphon most of the fuel out and leave it at that.

Anyway, I'll get Freescan running again and try to reset the fault code (engine off, ignition on). For all I know, the problem may have gone (maybe water in the tank sank to the bottom where the pump pickup was and perhaps it's all gone now).

Quote

as long as the knock counts aren't increasing, then it is usually just a little transient issue upon startup.  Not a problem, and pretty common on the Esprit.

This is the part I don't understand. I'm getting a fixed value of 12 knocks at various rpms. I wouldn't regard this as "transient", unless Freescan is recording the count on startup and displaying that value until a greater number of counts are sensed.

Quote

The sensor wire is easy to knock loose... during an oil change or other work.

Been there, done that!

Quote

The knock sensor must also not be torqued in too tight, or too loose.  I think the spec is 14 ft-lbs. 

Thanks, I'll look into that (although they're not the easiest of sensors to get to).

 

Much appreciated, guys.

Cheers

Ian.

[DanR]

Ian, I've got the oem Tech 1 diagnostic kit so it would be interesting to compare it to your freescan. Do you ever get over to this side of Sydney. I'm retired too so easy to organise a time.

[sailorbob]

Error code 43 is flagged for two possible reasons:

1 - The ESC input signal has been in a low logic state for a period of time greater than the KKESCP parameter value during a 3.9 second time period (the stock SE value for KKESCP is 3.67 seconds) and an open circuit or short circuit to ground is indicated.

2 - An open circuit or short circuit to ground has been indicated for a period of time greater than the  KK43ATIM parameter value (the stock SE value for KK43ATIM is 5 seconds).

[Vulcan Grey]

@Qavion  The knock counts are incremental from each engine start.  It starts at zero and then increases from there.  So if it goes up to ~12 in the first 1s and then does not increase after that, until the engine is shut off, then it is pretty normal.  If the number keeps increasing as the engine is running, and the ECU is also pulling spark timing (knock retard) to prevent knock... then that is a serious issue.

 

Qavion

[Qavion]

Quote

The knock counts are incremental from each engine start.  It starts at zero and then increases from there.

 Thanks, Travis. So the 0~250 range mentioned in the Freescan manual is simply a result of Freescan counting limitations? I previously assumed it would be impossible to get more knocks than this in a five second time frame. 

@Sailorbob/Derek

Thanks... er... still trying to process this information

I see mini oscilloscopes are getting really cheap these days (U$85 plus postage). I might buy one and have a look at the signal generated by the knock sensor. This one looks interesting...

Might also be good for diagnosing electronic speedo/tacho problems

@DanR

PM sent (and received, I see)

I see knock sensors seem to be readily available (e.g. at RockAuto ACDELCO P/N 21391 (21-391))

Cheers

Ian.

 

 

[Bibs]

Have you put new petrol in the car yet? 

Do that, start the car then when it's running start freescan and go for a drive. After the drive, note zero knocks and move on. 

[sailorbob]

Any spark retard due to knock is calculated using the change in knock count value so a high knock count does not automatically mean spark is being retarded.

[Qavion]

Quote

Any spark retard due to knock is calculated using the change in knock count value so a high knock count does not automatically mean spark is being retarded.

Thanks, Derek & Bibs

I haven't yet had the chance to drain the fuel, but ran the car at idle today to see if the CEL returned after resetting the recorded faults in Freescan. It didn't. I have almost half a tank of fuel, so it won't be easy to drain. I'll have to book the car in at a local garage.

Freescan showed 15 knocks on start with a cold engine, but nil further after that. Further starts with the engine warm produced 7 knocks (none further).

The engine, at any rpms, does show intermittent stumbles, but I'll wait until I can put new fuel in the car before trying to diagnose that.

Cheers

Ian.

[Bibs]

The knocks being detected on startup aren't knocks per se. The knock sensor is just a microphone of sorts and it's reacting to the startup of the engine, not knocks in the cylinders which is why those ones can be completely ignored. That's why I told you to start the engine and then start freescan, then you'll see if there are any real pre-detonations happening. 

[Qavion]

Ran the engine again today with a new laptop (with a serial to USB adaptor). Unfortunately, the results I'm getting still don't make any sense.

If I start the engine with Freescan running, I get a fixed value of 12 to 15 knocks. If I start Freescan after starting the engine, I get around 6 or 7 knocks (engine warm or cold). It doesn't get any bigger or smaller.

If the knock count was averaged over a certain time period and frozen at the max value, the numbers would make sense.

I can't see how a faulty knock sensor would cause this either (If it put out a false knock signal, wouldn't the value increment?)

Curiouser and curiouser...

 

(EDIT: I have a new sensor. Perhaps I should change it for peace of mind)

Edited May 14, 2016 by Qavion

[Qavion]

Update: Knock sensor replaced. Also, I changed the coil packs and ignition module. Fuel also replaced. I get the same strange knock results as before. e.g. Constant values of around 5/6 knocks if I start Freescan after starting the engine (the knock count doesn't get any bigger after that). The CEL hasn't returned (yay).

I'm starting to think that my ECU or serial/USB adaptor is adding a fixed amount of knocks.

Removing the old knock sensor was an epic task. I had to remove my oil filter (see other thread), intake plenum, coolant pipes, airfilter box and wiring to get proper access. The pressed steel knock sensor has a 22mm hex drive. The hex isn't square, but a little bit tapered (a 21mm socket almost fits), so you have to make sure you push down on the socket really hard as you move the ratchet or breaker bar. You can't put a big breaker bar in there because there is not enough room. The electrical contact on the top of the sensor means that you have to have a deep socket, but not too deep, otherwise the socket slips off (or use a hacksaw to cut off the electrical connector).  I bought 3 different types of 22mm socket before I found the right one.  I ended up using a 22mm semi-deep socket, ratchet adaptor and T-bar (with a sliding bar) with extensions on the bar plus a few days of lubing and heating the threads on the sensor. It literally took me several days before I was able to come up with an ideal removal technique.

My engine still has a strange intermittent wobble, but I think that's been there for the last 17 years (and for all I know, it might be standard SE behaviour). I've basically changed everything on the engine which might cause this. Anyway, it's not keeping me awake at night and the car goes like the clappers (as they say).

Edited June 16, 2016 by Qavion

[Chillidoggy]

Did you follow the service note diagnostic procedure that Barry posted? That would tell you if your ECU is faulty.

[Barrykearley]

You must go through the fault finding logically.

my old esprit had this and that swapped in the hope of fixing a guess. Trust me - it was all fixed cheaply and using correct logic. Do not use guess work

[Qavion]

I haven't yet run through the diagnostic chart. I replaced the ECU twice for another problem, so I hope it's not that.

I'll try something simple like checking the input voltage to the sensor and also tapping the engine block to see if the knock count goes up.

 

Thanks!

Cheers

[Qavion]

Working through the Fault Chart...

I have 5.0 volts at the knock sensor plug and when I hit the engine block, the knocks increment. I don't know if it's normal, but Freescan was only recording 1 knock for every two hits. Not 100% sure, but I think I had to hit the block twice in quick succession.

 

The CEL light hasn't returned. It's just the higher than normal Freescan initial knock reading which looks odd (I have seen 0~2 knocks a while ago, but I've changed two ECM's and an alternator regulator since then).

Given that the knock count is not incrementing during normal engine operation, I assume it's nothing to worry about (?)

Cheers

Ian

[Vulcan Grey]

correct 5-6 knocks is normal, and nothing to worry about if it isn't increasing.  Your knock test showed the sensor is working.

The knock sensor is sensitive to the torque used to tighten it to the block. If you torqued it too hard, then it would be possible to get to many knock counts.  Though, 5-6 is totally normal for an Esprit 910.

 

[Qavion]

Quote

The knock sensor is sensitive to the torque used to tighten it to the block.

Not sure what the old one was torqued to, but I made sure the new one was torqued as per the manual (17~21Nm)

Quote

 Though, 5-6 is totally normal for an Esprit

Thanks, Travis. I think I'll go with that.

Cheers

Ian.