How do I ground diagnostic terminal (ALDL connector)?

[Jwernatl]

Hey all - I installed a new HOLLEY tbi on my 878 v10.

I need to set the base idle. However reading from the drivability manual: STEP # 3 tells me to 'ground the aldl connector' -
and in STEP # 4, it says 'Remove ground from Diagnostic Terminal'

***
MINIMUM IDLE SPEED ADJUSTMENT - TBI 220
This adjustment should be performed, only when the throttle body assembly has been replaced. Engine should be at normal operating temperature, before making adjustment.

Adjust
1. Remove air cleaner, adapter, and gaskets. Discard gaskets.
2. Plug any vacuum line ports, as required.
3. With IAC valve connected, ground diagnostic terminal (ALDL connector).
4. Turn on ignition, do not start engine. Wait at least 30 seconds, (this allows IAC valve pintle to extend and seat in throttle body).
5. With ignition "ON”, disconnect IAC valve electrical connector.
6. Remove ground from Diagnostic Terminal and start engine.
7. Remove plug by first piercing it with awl, then, applying leverage (Figure 4-27).
8. Adjust idle stop screw, to obtain 700 rpm + 25 rpm 500-550 rpm in drive with automatic trans. and 600-650 rpm in neutral with manual trans. for 4.3L & V8 engines.
9. Turn ignition "OFF”, and reconnect IAC valve electrical connector.
10. Unplug any plugged vacuum line ports and install air cleaner, adapter, and new gaskets.

***

Thanks everyone - IM sure it's something simple- but cant figure for the life me - I believe Im over thinking it.

 

[Bextreme04]

Hey all - I installed a new HOLLEY tbi on my 878 v10.

I need to set the base idle. However reading from the drivability manual: STEP # 3 tells me to 'ground the aldl connector' -
and in STEP # 4, it says 'Remove ground from Diagnostic Terminal'

***
MINIMUM IDLE SPEED ADJUSTMENT - TBI 220
This adjustment should be performed, only when the throttle body assembly has been replaced. Engine should be at normal operating temperature, before making adjustment.

Adjust
1. Remove air cleaner, adapter, and gaskets. Discard gaskets.
2. Plug any vacuum line ports, as required.
3. With IAC valve connected, ground diagnostic terminal (ALDL connector).
4. Turn on ignition, do not start engine. Wait at least 30 seconds, (this allows IAC valve pintle to extend and seat in throttle body).
5. With ignition "ON”, disconnect IAC valve electrical connector.
6. Remove ground from Diagnostic Terminal and start engine.
7. Remove plug by first piercing it with awl, then, applying leverage (Figure 4-27).
8. Adjust idle stop screw, to obtain 700 rpm + 25 rpm 500-550 rpm in drive with automatic trans. and 600-650 rpm in neutral with manual trans. for 4.3L & V8 engines.
9. Turn ignition "OFF”, and reconnect IAC valve electrical connector.
10. Unplug any plugged vacuum line ports and install air cleaner, adapter, and new gaskets.

***

Thanks everyone - IM sure it's something simple- but cant figure for the life me - I believe Im over thinking it.

That's pretty bad instructions. You need to short pin A to Pin B on the ALDL connector. Pin A is ground, Pin B is the diagnostic data pin.

You must be registered for see images attach

 

[Jwernatl]

Well dang. That’s pretty ezpz.

For my own serenity, would you know why this would have to be done?

I’m not questioning if I should - of course I will.

Just wondering why. Understanding may help down the road.

 

[Matt69olds]

Grounding the ALDL will command the pcm to retract the IAC plunger, put the timing in static mode so you can set the minimum air.

Minimum air is the absolute lowest speed the engine should ever idle. Usually that speed is about a 100 rpm lower than what the engine normally idles. With the data link shorted to ground, the ignition timing is set to its base setting and won’t move (causing the idle speed to change) and ensures the IAC has enough “swing” to control engine speed regardless of temperature, load, or other factors.

 

[Snoots]

It takes the computer out of the loop. You don't want to be fighting the computer setting your baseline timing.

 

[Jwernatl]

It takes the computer out of the loop. You don't want to be fighting the computer setting your baseline timing.

Grounding the ALDL will command the pcm to retract the IAC plunger, put the timing in static mode so you can set the minimum air.

Minimum air is the absolute lowest speed the engine should ever idle. Usually that speed is about a 100 rpm lower than what the engine normally idles. With the data link shorted to ground, the ignition timing is set to its base setting and won’t move (causing the idle speed to change) and ensures the IAC has enough “swing” to control engine speed regardless of temperature, load, or other factors.

Thanks, guys... that all makes sense crazy simple too.

 

[AuroraGirl]

Thanks, guys... that all makes sense crazy simple too.

you can also disengage or engage your torque converter with it too while driving , view ECM fuel corrections as demonstrated by the flasihing frequency of the CEL, and maybe more

 

[Jwernatl]

That's pretty bad instructions. You need to short pin A to Pin B on the ALDL connector. Pin A is ground, Pin B is the diagnostic data pin.

You must be registered for see images attach

How do I short pin ‘a’ to ‘b’ on ADL - with a paper clip or jumper wire? I’m basically just connecting the two?

 

[Jwernatl]

I found it. A video proved that, I over think things.

 

[AuroraGirl]

I found it. A video proved that, I over think things.

a "fused jumper" is the "best" way to jump it, but a paperclip yes works fine

 

[Jwernatl]

Awesome- thank you- I found a video and it pretty good.

I have history with blowing the computer on an old JEEP. Soooo, I’m a little gun shy.

 

[AuroraGirl]

Awesome- thank you- I found a video and it pretty good.

I have history with blowing the computer on an old JEEP. Soooo, I’m a little gun shy.

a fused jumper may not be a bad idea(inline fuse holder that holds a glass fuse is the cheapest way, found at the auto store for a few buucks, and a low amp fuse put in) if you want to be safe lol.
One of the ALDL pins can be grounded to actuate a lockup converter /unlock if one has a lockup converter. but thats a different day diagnostic approach