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1993 A9L Pin 46 12V help

6K views 23 replies 3 participants last post by  splithigh 
#1 ·
93 Fox , T56 magnum, A9L with Tweecer RT

Car was an original AOD with C3W EEC (I still have C3W EEC). Swap was preformed by previous owner with T56 and A9L. I purchased the car and was fighting idle surge problems when cold and when restarting. Reviewed idle surge checklist - Checked voltages at MAF, TPS, IAC and replaced IAC and TPS, base idle reset,replaced all vacuum hoses. KOEO codes 15, 85, 67 and 66c. Eliminated 15 with check sum base set to 0 with Tweecer. 85 due to no purge installed, 67 is NSS so I started chasing this code. Still have 67 code with clutch in while running test. 66 may be due to car surging badly and low voltage as it almost dies (will diagnose further after I get it running again)

I could get the car idling well after battery disconnect, drive around for a while (20-30 min) with no issues. Restart minutes later and idle surge returns like there is no memory.

I have been researching many threads and I believe that I have narrowed down some issues.

I am getting 13v at pin 46. A9L disconnected (key on, crank, clutch in/out)

Car had a Auto O2 harness so I re-pinned the loop from NDS pin 30 to Manual on the black connector. (also tried NDS to auto with same result).
Car had a auto trans harness so I removed and installed a new manual trans harness with all 8 wires. T56 will only accept VSS and passenger side 4 wire plug from factory manual trans harness. plug or unpluged - have 13v at pin 46
black and gray clutch switches are installed at assembly. plugged, unplugged, and looped NSS with fuse - all still 13v at pin 46.
Car has push button start under dash (previous owner wired directly to ignition in engine compartment) key does not start car. (possible concern?)

disconnected all 46 connections per wiring diagrams, trans, NSS, clutch switch, tps, O2 harness, Baro, intake temp N/A, EGR N/A, engine coolant sensor N/A - checked pin 46 volts at each disconnect and with all disconnected - Still have 13v at pin 46

Removed pin 30 at EEC harness and grounded at chassis - Still have 13v at pin 46

I inspected the A9L and do not see any signs of burnt connections. Not sure how this did not originally fry the A9L as the car was running for years with auto harnesses (O2 and Trans). Most say that this will burn the EEC.

Any ideas on why I am still getting 13V at pin 46? Thank you for your help.
 
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#4 ·
I believe it comes from the ECU wire harness across the engine firewall and connects at the brown connector by the brake booster and then runs into the drivers side under the dash. Some wires (i.e. red/green) appear to go to the ignition. I tried uploading a picture (new to the forum) so I hope it worked. I read somewhere that one person had a faulty ignition and it fixed the 12v to pin issue.

Thank you for the A9L2 info. I ran across this while searching Tweecer tunes. Is there a way to tell if my ECU uses the GUFB strategy?

I am concerned about the 13v at pin 46 and don't want to hook up the ECU until I correct it.

Thank you for your help.
 

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#5 ·
I figured out my problem! My stupid mistake! I ran resistance test on all pins to the self test connector where pin 46 terminates and I had the harness flipped and was originally testing pin 15 which has power at start. If you flip the ecu harness 15 is in the same position as 46. Lesson learned, review diagrams closely for correct pin-outs.
 
#7 ·
Thanks Indy. I found out that I was testing the wrong pin as I had the harness flipped. Pin 46 has 0 voltage at start. I have the manual trans harness and repinned the O2 harness. Still getting code 67 so need to figure out pin 30 now. I have the NSS installed at the clutch pedal however 2 of the manual trans harness connectors do not mate to the T56 Magnum. May need to chase that scenario now to figure out how to connect all of the wires at the trans.
 
#8 ·
there is a NSS on the magnum?

the clutch pedal that the pawl switches is the clutch sense switch.

if not, you can turn off the logic for that in the ecm, with a tuning device
 
#9 ·
I am researching the plugs on the T56 Magnum. There is a plug on the passenger side with 4 pins (2 wires and a jumper wire). It appeared to go to the 4 pin plug on the manual trans harness. It also has the VSS by the speedo. The reverse lockout plug on the T56 does not match the manual harness plug so I have to check if there is an adapter plug available.

I have the Tweecer RT. Do you know which scalar disables the NSS? Possibly "Transmission Strategy"? Mine is set to "0". I am still fighting idle surge and I have been through the checklist. I ordered caps for the A9L as one had corrosion. Hopefully that fix will help.

I have read that code 67 can cause idle issues so I am chasing a fix for 67 which involves the NSS. The switch is installed and not jumpered. I read that I can ground pin 30 to see if this helps with the idle. I would like to fix this correctly.

Thank you for your help.
 
#10 ·
yes the scalar, transmission strategy is used to tell the ecm what switches you have, if any

does your idle just surge up? or does it oscillate to a stall, especially coming to a stop?
 
#11 ·
Oscillating to a stall. Hopefully it is just the code 67. I can set the idle after disconnecting the battery, drive around for 25 min just fine. Shut it off and when I restart hot or cold it surges again like the memory is lost. Or maybe it is the code 67 causing this. I also had code 66 low voltage to MAF but I think it might be due to the low idle surge (more to come when I get it running well to test accurately).

I was going to try to ground pin 30 and see if it clears up the idle. Should I pull the pin and ground the wire only or back probe the pin with the wire in the computer and ground that? Or turn off the scalar in the Tweecer?
 
#12 ·
Replaced the caps in the A9L. Grounded pin 30 to the chassis ground next to the ECU. Reset the idle and now the surge is gone. Strange thing though....when connecting pin 30 to ground using a heat shrink crimp connector, the car will fire and then die. Twisted the wires together with electrical tape and it runs fine. I have been driving for days now with no issues however, I do not like the twisted wire fix. I am planning to solder the wires to see if that affects the fire/die scenario.
 
#18 ·
They are currently installed at the clutch pedal.

Trying to troubleshoot my surging, I researched threads and determined that the car had the auto trans harness and auto setup for the O2 harness. I replaced the trans harness with the manual version and repinned the O2 harness for manual. Still had idle surge so I tried grounding pin 30 and it cleaned up the idle. There may be an issue with pin 30 wire to the switches or the switch assembly.
 
#19 ·
why would you think this is a cause for surge?

the reason for surge is the idle cannot be controlled, because ecm is moving spark and IAC duty cycle according to a incorrect idle air mass, that is measured by the maf

this is usually because people play with the throttle stop

the ecm is expecting an exact air mass with the throttle closed, it is a scalar

once the rpm is outside acceptable rpm value, spark and IAC are dropped fast, this causes a dying engine, then a response of IAC and spark, goes up, and shoots the rpm above the limit again

this cycle will continue, until a stall, or you step on the air throttle
 
#20 ·
I thought the reason for the surge was that the car was wired as an auto with a manual trans which may affect the ECU seeing a non-neutral condition. I believe pin 30 is not wired to the clutch and NSS as it may be still setup in the auto trans configuration. I tested for voltage at pin 30 and had 0V with key on and crank. Temporarily grounding pin 30 fixed code 67 and the idle was better so I think that the current wire path for pin 30 may be be incorrect or the clutch switch/NSS is bad. I still have to confirm this.

The surging did get worse after I adjusted the idle trying to fix the surge (user error on my part). I did check the IAC and it was filthy. I cleaned it and then decided to replace it with a new Motorcraft unit. I was getting code 66 which I have to troubleshoot next.

Based on my recent research on tuning with the Tweecer, I am finding that there may be a few settings that may be incorrect or could be adjusted better. Some of these may be affecting the idle. I am still reading up on all of the settings.

Checksum base is 8192 which is throwing code 15.
Idle is set to 672 (was told this should be higher with my setup, maybe 800-850).
ISC startup rpm adder was 16 rpm's with a time of 80 seconds (seems odd).
MAF voltage minimum is set to .366 (many say to reduce this to .125 or lower).

If some settings are incorrect, I am concerned there may be others.

Thank you for providing insight on idle surge cause/effect. I appreciate your help.
 
#21 ·
you should correct the wiring

get everything correct

then start tuning, you obviously have a modified engine

I suggest you head over to efituning and start reading the write ups
 
#23 ·
If you still have surging after trying to remedy

I can tell you what PIDs to log, and you will see the logic, and what needs to be changed

It took me years to figure it out
 
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