Service Engine light

[Guest imported_blazer1997]

Sorry guys I'm back. Out today enjoying my reatta, and stopped for light and car starts surging forward drop it in neutral engine smooth again. Back in drive start all over again.

Drove home found no codes at all at ecm or bcm. But on the ecm side had a old pa3 which is a knock signal been there over 3yrs but today showed up pa3-276 ed 17

Found that ed 17 refers to knock signal then in the service manual stated esc which stand for electronic spark control.

What does the (276)refer to?

Could knock signal cause the surging at idle? Thanks

[2seater]

The knock signal is a number that increases over time if knock is, or has been, present. Essentially it keeps a record of the knock counts over time and will increment upwards until it resets, or rolls over to start at the beginning again. It is not unusual to get some knock counts on start up so it is normal for the counts to increase when you take a look at it from one day to the next. It is not normal for it to increase with the engine idling in gear. Substantial knock counts will trigger the ECM to retard timing, reducing engine performance. In many cases you can cause the engine to stumble by giving the engine a sharp rap with a hammer or even a large wrench while idling which will trigger the knock sensor. If severe enough it will retard timing momentarily. The easiest would be to drive the car and monitor a few sensors to see what might be happening. Knock counts, spark retard or the spark timing can be monitored to see if there is something going on when the engine acts up. If nothing turns up, engine knock is probably not the problem and the solution is elsewhere.

[Guest imported_blazer1997]

I have replaced every sensor except this one knock sensor give it a try.

Fuel pump, and screen replaced last week.

Thanks for the info.

[Guest imported_blazer1997]

Will a knock sensor cause a engine to surge????

[Guest imported_blazer1997]

Can anyone give me the location of the knock sensor on a 89 reatta? Thanks

[Machiner 55]

Knock Sensor. See Attachment.

[Machiner 55]

looks like this:

$ between $30.00 & $50.00 new.

[Guest imported_blazer1997]

reatta John nice diagram of engine, and sensor. I found this morning the knock sensor would not cause the surging of the engine. Oxygen sensor at idle was all over the place from 0.03 to 0.88 under warranty changed it out no change.

Took the egr valve off, and took it apart and cleaned it still no change.

I have checked, and checked for vacuum leak none to be found.

So what ever the problem is keep driving it till it becomes more evident or stops running.

Figured up my total on this problem over $600.00 right now.

On the crt screen going to ECM going thru every thing the oxygen sensor down arrow at bottom of the screen continues to flash regardless if looking at TPS or RPM is this right???

[Guest imported_blazer1997]

List of ECM codes with car in drive sitting still.

ED 01 TPS 0.32

RD 04 Coolant 98*

ED 06 MS Inj PW 4.1 to 5.5

ED 07 Oxy Sensor 0.08

ED 08 Deg Spark 26*

ED 10 Battery Volts 13.8

ED 11 Rpm 644 to 747

ED 16 Spk Angle 0*

ED 17 Old Pa 3 166

ED 18 Cross Cts 0

ED 19 Int Fuel 155

ED 20 Blm Fuel 21

ED 21 Air Flow 3.4 to 3.9

ED 23 Matt ED 98 25* 131 Ign Cycles

ED 99 Prom ID 864

If anyone can see anything out of place please let me know. Thanks

[harry yarnell]

The oxygen sensor is SUPPOSED to vary from low to high (.2-.9). that shows it's working. If it stays the same, then either the sensor's bad or there's mixture issues.

[padgett]

Temp is high (over 200F) and BLM is waaay low - could it have been 121 ? Was the engine running ?

Ignore O2 and look at crosscounts - will be low but some at idle and more when driving. Zero is not good. Coupled with the BLM (if real) I suspect the O2 sensor (or circuit) is bad.

TPS is low also, should be .38-.42 with foot off gas and over 4.0 at WOT (foot to floor)

[Guest imported_blazer1997]

Padgett this is what i have now after re-checking. ED20 Blm in park accelerating got 150.

Crosscounts at idle 0 In gear 0 in park accelerating up to 2500rpms got 3 to 10.

Thanks very much. Need all the help, and interest in this problem that I can get. Larry

[Guest imported_blazer1997]

Making me read Padgett just kidding.

ED 18 The oxygen sensor cross counts is displayed as the number of times the o2 sensor crossed the reference line each second. This is a new oxygen sensor as of this date 03/08/07 under warranty. and it does increase under acceleration, and decreased. So think the new oxygen sensor working OK.

ED20 The block learn multiplier (BLM Fuel) is displayed in counts, from 0 to 255. Re-checking it is Showing 150 at idle or in park giving acceleration up to 2500 rps stays the same 150, but let off the acceleration drops to 144 and then returns to 150 at idle.

This ed20 brake this down in plain english.

[padgett]

OK the computer has to "learn" what the proper mixture setting is for the engine (starts out with a "generic" baseline mapping.

The operating range is really a contour map of estimated load vs rpm (with a temperature factor thrown in) and the output is an injector pulse width (also calculates the spark advance but that is seperate).

As the engine runs it uses the O2 sensor feedback to calulate whether the engine is running rich or lean and tosses in a fudge factor to compensate via two additional maps - the "instantaneous" (Fuel Integrator - INT) and the "block learn mode" (BLM).

OK the nominal (baseline) is 128 (binary midpoint) and that is what you want to see across the board +/- about 5 counts. A higher number means that it has sensed a lean mixture and is adding counts (injector pulse width) to compensate.

Now the instantaneous is the first correction and changes often. If a particular instantaneous correction is needed for a long time it is moved to the BLM and the instantaneous goes back to 128 for that cell (particular rpm vs load value).

So BLM indicates the long term correction and "instantaneous" is Right Now. A BLM of 150 means that the computer is richening up the mixture to correct for a long term lean condition at thet particular operating point.

Disconnecting the battery for a while clears the BLM map and you can then watch the "instantanous" to see how the engine is actually operating but after a period of time the base change will move to the BLM and instantaneous will return to around 128.

So the actual mixture (injector pulse width) is controlled by the base setting + (BLM-128) + (instantaneous-128) all times a correction factor.

Values of either BLM or Instantaneous above 128 = more gas (lean detected) and Below = less gas (rich detected). So for high numbers look for things that either cause or sense a lean condition (dirty injectors, bad O2 sensor) particularly if they stay the same pretty much across the rpm and load range.

What you are seeing is not going to set any codes except if there are no cross counts but what you reported sounds low - at idle I would expect 2-6 and over 12 when driving. The 150 sounds marginally high (compensating for a lean mixture) to me but is within the normal range. Is your tailpipe sooty ?

[2seater]

I know you have been checking for vacuum leaks but have you checked around the PCV valve at the right rear of the intake manifold? Padgetts explanation is spot on and trying a reset to make the ECM start over is a good idea. In a stock system 150 is about the limit of how far the BLM can adjust, and while the number difference from the desired 128 looks large, it is really only a few percent on the actual fuel delivery. Two other things can tell the the O2 sensor the engine is lean when it really isn't is a crack in the exhaust manifold, especially the rear one, or a misfire. You would think the cylinder that doesn't fire would read rich but that isn't really true, the oxygen isn't consumed even though there is excess fuel present. My personal experience is that the O2 sensor can get too cool after an extended idle and it will "go out", particularly if the engine is running rich (the opposite of what the BLM is saying). If you bring the idle up to about 1500 rpm for 30 seconds or so should get the cross counts back. One other thing is I have not had very good luck with Bosch O2 sensors. It isn't that they don't work, but they just seem lazier than a Delco or even a Neihoff or Standard brand? They may even be made by the same companies, but that has been my experience. No joy with Bosch platinum plugs either. I don't know why, but perhaps it has to do with the waste spark system we use that fires half of the plugs with reverse polarity?

[Guest imported_blazer1997]

Padgett thank for the info. Yes the tailpipe is black, and can smell rich mixture. Just replaced the ecm NEW from gm dealership also all gm parts are tcp, PCV, Maf,oxygen sensor, plugs, plug-wires, fuel pump and screen, fuel filter, EGR cleaned with all new gaskets. Injectors cleaned,and checked for leak-down spray pattern, pulse flow, pulse volume, static flow pulse volume, pound-per-hour flow was 19.24 on all 6 injectors.

Tomorrow morning disconnect the battery cables and try again.

If this doesn't help where should I go from here?

[padgett]

Could be that you have a "factory defective" O2 sensor. Buy a second and at worst you will have a spare (I change every time plugs are changed). Use only Delco AFS-20 (2516293) sensors.

ps if the BLM maxes without curing the problem, the Integrator will be off as well.

[Guest imported_blazer1997]

This morning removed, and re-connected the battery cables after 1/2 hr.

Hit the express-way at 61 MPH ED-20 BLM Fuel read ( 136 )

ED-18 at 60MPH read ( 5 ) RPM was at 1678

Returned home in driveway in gear stopped started surging.

This engine is extremely quite, and very responsive from dead stop to top end.

Guess monday get the 3rd oxygen sensor and try it. Padgett thanks for part #

[Guest imported_blazer1997]

Mr. Padgett need your expertise on the ECM status service mode.

On page 8D-5 and 8D-6 of the service manual #3 states the OXY status indicator is turned ON whenever the oxygen

sensor signal to the ECM indicates a "rich" exhaust condition. This light should switch between "rich" and

"lean" (flash "On and Off" during warm steady throttle operation.

This is what I have. It will stay on at idle, and at operating temp will flash on and off when

giving steady throttle.

When I check other ED locations it will never move from the oxygen status indicator position.

Is this normal or inditating a problem?

[Guest imported_blazer1997]

I guess everyone has exhausted all their mechanical skills regarding my problem. I have also gave up.

[padgett]

No, just not paying attention (I do have a day job). I would expect at least 12 and maybe more at 60 mph when warmed up. 5 sounds very low. (now I am going to have to look). Is the MPG poor (one of the nice things about the CRT is you can watch both instantaneous and average mpg)?

[Guest imported_blazer1997]

Thanks Padgett. Love be able work again but after 2 open-heart surgery's not able.

[padgett]

Well my memory was faulty - on a five mile trip after the engine warmed up I observed 3-8 counts (varies) at 47 mph cruise (lockup/O/D). 1-4 when coasting and up to 12 when accellerating. This is with a year-old Delco O2 sensor. Was alone in car so could not get a complete set of readings.