My ECM has no wire to park/neutral input on ECM and no switch either?

[Kai]

Hello Forum, I got a 92 silverado 305 5.0 automatic with a 16146299 AWHD ECM. Was having alot of idling issues. High idle in park and drive etc. I replaced speed sensor due to fluid leak and just because it's an old truck. So, idling is a whole lot better now. However idling it is in the low side both in park and drive. Come to find out that there is no park/neutral switch that I can find. There is a reverse switch in the bottom end of steering column. Don't think its in tranny as there is only a speed sensor and possibly a 3 wire TCC switch. Problem also is that there is no wire going to the park/neutral signal into the ECM. Should be the B10 input on ECM and there is no wire there. I could not even find the plug for the park/neutral switch. So not sure where to go from here. Doesn't it need this input to control idle. I also put me meter to the B10 input and there is 13 volts on there, this line should go to ground when in park or neutral. So I believe the ECM thinks it's always in drive. It also idles lower in drive than in park or neutral. Where to from here? Thanks.

[tayto]

it is in the switch on the steering column, NSS or neutral safety/ range switch. should be 2 sets of contacts one for allowing voltage to the starter when in park/neutral and the other to send signal to the ECM. there should also be a terminal for the reverse lights. You might need to drop the column to access this switch by removing th3 2 nuts under the dash. have you confirmed with a scan tool? there should be no voltage there. are you referencing ground when you check this (continuity) or are you referencing battery voltage?

[Kai]

The switch on the column only has 2 pins. I confirmed that this switch is for the back up lights and they are working. When I connect tuner pro on, it always indicates that it is in drive. I checked the pin on ECM by connecting meter to ground (metal in vehicle) and positive to the B10 pin where the safety switch should go to and it is reading battery voltage.

[tayto]

AWHD is a manual transmission calibration. looks like someone has done an automatic swap. You will need to get the correct NSS and wire it in as well as the correct calibration (AWHC). You could also upgrade to the newer TBI PCM, but will need a custom calibration made to work with your 700R4. Finding a complete and correct dash harness is the route i would go here from the wrecker.

EDIT: i also would bet your TCC isn't functioning. is there even wiring for it there?

[Kai]

Wow, I was think that myself. Putting a switch in and wiring it to ECM is not a problem. Not sure about the rest of it as far as calibration goes. Is the AWHC calibration mean I have to burn it into the PROM. Is the TBI PCM a new ECM that would plug in replacing my ECM. Would it fit existing plugs. My ECM currently has 1-24 pin plug and 1-32 pin plug. The only other connection I could find on tranny other than the speed sensor is a 3 wire connection going into tranny close to speed sensor. That is a 3 wire connection. I believe it's the TCC solenoid switch.
Why would I be reading 13 volts on the ECM pin B10 where the neutral/safety switch would go?

[mihela]

Should be very easy to tell if it was a manual truck before. Just see if someone blocked off the hole in the floor for the shifter. They aren't cut out there on an auto.

[Fast355]

Wow, I was think that myself. Putting a switch in and wiring it to ECM is not a problem. Not sure about the rest of it as far as calibration goes. Is the AWHC calibration mean I have to burn it into the PROM. Is the TBI PCM a new ECM that would plug in replacing my ECM. Would it fit existing plugs. My ECM currently has 1-24 pin plug and 1-32 pin plug. The only other connection I could find on tranny other than the speed sensor is a 3 wire connection going into tranny close to speed sensor. That is a 3 wire connection. I believe it's the TCC solenoid switch.
Why would I be reading 13 volts on the ECM pin B10 where the neutral/safety switch would go?

You are reading 13v because the ECM has a pull up resistor and the Park/Neutral switch grounds the pin pulling the signal low.

[Kai]

Yes, so can I just install a NSS and run wire to ECM or is there more to it than that if ECM is for a manual trans and not automatic.

[Kai]

Thanks mihela, I will check for that.

[tayto]

You will need to find an AWHC memcal but probably an easier solution is to get an adapter and get a chip burned.

For the newer PCM you need to repin the connectors. You will also need a custom chip burned to work with your 700R4. You will also still need to add the missing NSS and associated wiring. I have done a few stock engine PCM swaps and they run noticeably smoother FWIW...

[Kai]

I am new to tunning. All I have now is TunerPro RT and a transistor/resistor circuit for data logging on OBD1. I can wire in a new switch and connect to ECM. I am curious as to how I have been driving this truck like this for 2 years. At any rate found this on the pcm hacking site
16146299
Application:
1992 truck 4.3 V6 TBI “Z” LB4
1992 truck 5.0 V8 TBI “H” L03
1992-93 truck 5.7 V8 TBI “K” L05 w/o 4L80E
MEMPAK IDs: “Z”: …
“H”: AWHD, …
“K”: AWLC, …
CALPAK IDs: …
Program ID: 153 ($99)
Pgm ID Addr: $D004
Scan ID Addr: $D002:$D003
EPROM type: 2732
EPROM offset: $D000

My VIN has the "H" on it. I also downloaded the AWHC BIN file from this site. Can this be used to recalibrate or burn new or existing chip. Also do I need a new ECM as this one is working. Thanks for your help, just want to figure all this out and get truck running better.

[tayto]

no you shouldn't need a new ECM. not sure what you are using for chip burning equipment but that will determine if you need an adapter if using a newer style chip.

[Kai]

At the moment I don't have any chip burning hardware, but I may be able to borrow one. Is the AWHC BIN file all that I would need to burn into the memory chip. Is that all that needs to be done other than adding a NSS switch and wiring into ECM. Are there any other possible issues or will I have to do some tunning to it. If I can just download what factory calibration came with truck, that would be great as I don't want to fight it with my lack of experience in tunning. I can open up ECM to see if mem chip is socketed. Is there 1 mem chip in ECM or 2.

[stew86MCSS396]

Ironically bro's truck is a '92 5.0L '299 5 speed AWHD swapped to a 5.7L vortec heads L98 cam '7747 pin for pin but still sporting the 5 speed yada yada...

Like to offer these suggestions but with a word of caution as I never like to go to that "point of no return," meaning keeping your stock stuff to fall back on and perhaps doing suggested modifications on a spare.

Anyhoo...sounds like all you need is a bone stock AWHC.bin to get you going and a NSS. Not unheard of to let the ECM think it's always in drive as that's what people do when swapping into an older non-NSS equipped vehicle. Not sure how hard it is to source blank stock 2732a PROMs and not all burners can write to them. i.e. Moates Burn2 Autoprom APU1 These 2732a PROMs require a UV eraser to erase the bin that's written or a week in direct sun light works, too. 2732a can be problematic when being written to. I was getting purdy frustrated when it would consistently fail being written to 2 out of 3 times with 30-45 minute UV erasing sessions in between each attempt.

Other suggestion is to modify the ECM to accept the newer EEPROM but I'm purdy sure you won't be able to find one in a 24 pin so I suggest you modify the ECM to accept a 28 pin EEPROM... http://www.gearhead-efi.com/Fuel-Inj...sion-(27SF512)

As mentioned, '7747 is a pin for pin swap so if you can locate a reasonably cost with an auto.bin should be plug and play and the perfect candidate if you choose to take a soldering iron to it.

[Kai]

Thanks for reply, may be a while before I do anything due to funds. As truck is running, may just leave it like that for now. Did check Futurlec and it looks like they do have the 2732a and the 27SF512. As for the 7747 by this do you mean acquiring a ECM 1227747 with auto bin and adding a park/neutral switch to ECM.