1990 Ford F-150 4x4 5.0 Manual 97k miles

I am troubleshooting 2 problems, and I wanted to pull codes before I got too far along. When I try using EEC self test procedure the CEL comes on and stays on. No flashes.
Ive bridged STI to STO.
Ive grounded STI to negative battery terminal.
Ive grounded STI to body ground after cleaning it thoroughly.

The 2 other problems I’m trying to fix.

1
Intermittent high idle / uncontrolled acceleration.
Occasionally when shifting into neutral the rpms will spike to ~3000 and stay high.
When truck is experiencing this problem it will sometimes accelerate without my foot on the gas (very unnerving)
I cleaned old IAC and reinstalled. Conditioned worsened.
I replaced IAC with new duramax. Condition improved but didn’t fix completely.
I replaced throttle cable because a plastic part near the throttle assembly was broken.
Vacuum leak?

2.
Engine dies when turning at low speed if I don’t keep rpm up. There is a leak in power steering line at a sensor in-line between the power steering pump and the steering assembly. It is my understanding that this engine does not give power steering enough juice at idle so sensor increases rpm.
keeping fluid topped up makes issue better but doesn’t fix it completely.
What is involved in replacing that sensor?

 

I would invest in an INNOVA 3145 code tester its only 30 dollars and it should get the EEC to test correctly. If your power steering pump is causing the engine to die then its putting a lot of drag on the engine i would see if it needs to be replaced.

 

Incorrect bridging and incorrect STI to ground, don't do that.

If your using a test light or analog voltmeter, that gets connected to Self Test Output(STO) and ground(negative).
Sensor Signal Return(SIG RTN) pin #2 gets bridged to Signal Test Input(STI).
Nothing should be connected to ground, except your voltmeter or test light.

 

It's okay to ground STI to the battery negative terminal. It's not going to hurt anything. Pin 2, Signal Return, on the self test connector is the same ground point as the negative terminal of the battery. If you do use Pin 2 and you cannot get the self test to start try using the negative terminal of the battery. If that works then you have an open circuit between Pin 2 on the self test connector and computer. That has happened more than a few times.

 

Thank you all for the quick responses. I’ve been using an old link I found on this forum to run this test and I’ll admit it has me a little confused.

https://www.fullsizebronco.com/threa.../#post-4271738

I made the correction and bridged STI to Pin 2. Still won’t run self test. CEL and battery light stay on.
I have tried connecting STI to negative with the same result. What’s next? Connect pin 2 to negative terminal?

 

If you cannot get the Key On Engine Off (KOEO) tests and stored code display to initiate then you may have a bad computer. Remove it then open it for inspection.

I see no reason to jumper jumper Pin 2 on the self test connector to the negative terminal of the battery.