possible ESC problems?????

[fxracer20v]

Sorry for the super long NOVEL i just wrote. Hopefully someone can help me.

i have a 87 GN in my shop and have been having problems with the timing retarding dramaticly. acctually let me start from the begining. customer brought it in comlaining of low power. test drove the car and it did't make any boost till the upper RPM range. by that time it was shiffing to the next gear. i put it on the dyno, did a pull and noticed it had low boost. then figured out the wastgate was faulty and opening very early and fluctuating alot. ordered a new adjustable wastegate and hose assy, installed them, now i have normal turbo reaction. boost comes on normaly and holds. after the install it now has a new problem. boost comes on, it starts to pull hard then power falls off but i still have consistend boost preasure. now with scanner hooked up (new snap-on scanner, not the scanmaster), key on, engine off i get a knock reading of 0 like i should. after starting the car it doesnt stay at zero. after every start i get a different number, 89, 43,28,106, etc.which is representing some sort of knock signal not actuall knock retard. i know these numbers probably make no sense because im using a snap-on scanner and not a scanmaster which u guys are used to. i unplugged the knock sensor and cautiously did another pull on the dyno. same thing. i then unplugged the ESC. check engine light came on like it should but i now read 0 all the time. i again did another cautious pull and now have a ton of power. i plugged the module back in and the problem came back. QUICK note, there was only one instance when i started the car and the scanner read 0, so i did a pull and i had full power. i shut the car off, restarted it and the problem was there again. this only happened once. i have a TSB relating to the ESC module in my computer which leads me to think it might be the culprit. now that u have read my NOVEL my question is, does any one have instructions on checking the ESC module or have any other ideas. i have checked everything else, fuel preassure, etc. i know it has something to do with the timing retarding on me. before i sell my customer a really expensive ESC module i want to bee 100% sure its the problem. again sorry for the super long NOVEl and thanks in advance for any/all replies and help.

 

[mikestertwo]

It's rare that module goes bad. What your most likey seeing is false knock coming from some other source. Need more info on the car. Is it all stock? What chip is in it? What mods does it have? Assuming the knock is false it could be coming from the down pipe touching the frame, cracked flexplate, valve train noise, ect.

 

[SHADOWII]

The MAF....

sensor has been known to create weird problems when bad and it appears to be connected to pin "B" of the esc. Also, are you clearing the codes from the ecm before each check?
With no knock, the esc sends a voltage of 8-10v tothe ecm on pin b-7 on yel/blk wire 457 from pin c of the esc.
With knock, the esc turns off the voltages to the ecm.
Have you tried tapping the block w/the engine running to see if it responds. the rpms should drop and the knock signal should increase, and the ecm should retard the timeing thru the est. the k/sensor output is measured in a/c volts, on pin e of the esc, dk blue wire 496.
as a side note pin d, the blk/wht wire goes to grd. on the esc.
I think if it responds to tapping by the knock-sensor, the problem is else where. maybe false knock thru the wires from the ignition, etc. Hope this helps.

 

[Chuck Leeper]

Knok sensor torqued to spec??

 

[TurboBuRick]

ELECTRONIC SPARK CONTROL (ESC) CIRCUIT
3.0L “N“ SERIES; 3.8L “A, C & H” SERIES
3.8L TURBO “G“ SERIES (PORT)
Circuit Description:
The ESC svstem is ComDrised of a knock sensor and an ESC module.
The ESC iodule sends ‘a voltage simal(8 to 10 volts) to the ECM. ~ When the sensor detects detonitiog, the-module turns “OFF” the circuit to the ECM and the vo tage at ECl
terminal “B7” drops to 0 volts. The ECM then retards EST as much as 20” in one (1) degree increments, to
reduce detonation. This happens fast and fre uently enough that if looking at this signal with a DVM, you
A loss of the knock sensor signal or a loss of ground at the ESC module would cause the signal at the ECM to
remain high. The ECM would control ignition timing (EST) as if no detonation were occuring. The EST would
not be retarded, and detonation could become severe enough under heavy engine load conditions to result in preignition
and tential engine damage.
Loss of tc ESC signal to the ECM would cause the ECM to constantly retard the EST to its max retard of
20” from the spark table. This could result in sluggish performance and cause a Code 43 to set.
Code 43 will set when:
0 EngineRunning. 0 ESC input signal has been low more than 2.2 seconds.
Test Description: Step numbers refer to step Diagnostic Aids: An i n t e r m i t t e n t may be
numbers on diagnostic chart. caused by a poor connection, rubbed through wire
1. If the ECM Data (Knock Signal) display is insulation or a wire brokeninside the insulation.
fluctuating widely, the ECM is monitoring a low CheckFor:
voltage signal on circuit (457) at ECM terminal 0 Poor Connection or Damaged Harness Inspect
“B7”. ECM harness connectors for backed out terminal
2. Probing ESC harness terminal “C” with a test “B7”, improper mating, broken locks, improperly
li ht connected to 12 volts should result in the formed or damaged terminals, poor terminal to
“8LD PA3” (knock signal) displa wire connection and damaged harness.
checks out OK,“Scan” Knock Signal (OLD PA3)
while moving related connectors and wiring
harness. If the failure is induced, the Knock
Signal display will change. This may help to
isolate the location of the malfunction.
won’t see 0 volts, but an average voltage somew x at less than what is normal with no detonation.
steady reading due to Over 8 0 Intermittent Test If connections and harness
a plied to ECM terminal “B7”
3. I P over 6 volts is measured at ECM terminal “B7”,
CKT 457 is OK and the fault is due to a poor
connection at the ECM or the ECM is faulty.​

 

[fxracer20v]

WOW!! thanks for all the input. greatly appreciated, the car seems to be stock except for exhaust and intake. the chip in the ECM apeers stock, no sticker or marking to think it is aftermarket. i asked the customer about any mods and he told me he bought it just the way it is. now with all the replies from you guys i will be checking quie a bit of stuff this week on it. i did try the tap test with the hammer for giggles and it did nothing, i think because im already getting a knock signal from somewhere else. now that you guys have given me a lot of info there is more stuff i can check now. i will be double checking my voltages and ohm checks, also try unplugging other things to see if i get any other changes. thanks agian for the help and if anyone has anymore input that would be greatly appreciated too.