How do I work around a poor ground on the EEC-IV Test Connector?

Disconnect the vehicle's single-pin Test Connector from the Scan Tool (leaving the six-pin Test Connector connected), then route a jumper wire from the single-pin Test Connector to the battery negative post or a known good ground, such as a clean spot on the vehicle's metal frame.

Do I disconnect both diagnostic connectors from the Scan Tool?

No. Only disconnect the single-pin Test Connector; leave the six-pin Test Connector connected to the Scan Tool.

What test do I run after installing the jumper wire?

Proceed with the KOEO Self-Test according to the instructions in the Scan Tool Owner's Manual.

What can I use as a ground point for the jumper wire?

Either the vehicle's battery negative post or a known good ground — a clean spot on the vehicle's metal frame.

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Ford EEC-IV Self-Test Poor Ground Fix - Test Connector Jumper Wire Procedure

Service procedure text with figure for grounding the EEC-IV scan tool test connector to the battery for KOEO self-test

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Step-by-step service procedure for re-grounding an EEC-IV scan tool single-pin test connector to the battery negative post to run a KOEO self-test.

AI caption December 2009 · Photo 832 of 2216

This document is a troubleshooting note (formatted as an answer, "A:") addressing a common problem on Ford vehicles equipped with EEC-IV computer systems: a poor ground on the vehicle's Test Connector ground circuit, which prevents a Scan Tool from initiating the Self-Test. The document attributes the poor ground to bad ground point connections, worn or corroded wiring, or poor connector-to-wire contacts. It provides a three-step workaround: (1) disconnect the vehicle's single-pin Test Connector from the Scan Tool while leaving the six-pin Test Connector attached; (2) run a jumper wire from the single-pin Test Connector directly to the battery negative post or another known good ground, such as a clean spot on the vehicle's metal frame; and (3) proceed with the KOEO (Key On Engine Off) Self-Test per the Scan Tool Owner's Manual. An illustration shows the jumper wire routed from the single-pin connector to the battery negative terminal, with the six-pin diagnostic connector plugged into a Ford-branded scan tool. A reader learns how to bypass a faulty diagnostic ground so that self-test diagnostic codes can be retrieved. No specific years, models, or part numbers are stated in the document.

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Frequently asked questions

Why won't my Scan Tool initiate the EEC-IV Self-Test?: The vehicle's Test Connector ground circuit may have a poor ground, generally caused by bad ground point connections, worn or corroded wiring, or poor connector-to-wire contacts. These conditions prevent the Scan Tool from initiating the Self-Test.
How do I work around a poor ground on the EEC-IV Test Connector?: Disconnect the vehicle's single-pin Test Connector from the Scan Tool (leaving the six-pin Test Connector connected), then route a jumper wire from the single-pin Test Connector to the battery negative post or a known good ground, such as a clean spot on the vehicle's metal frame.
Do I disconnect both diagnostic connectors from the Scan Tool?: No. Only disconnect the single-pin Test Connector; leave the six-pin Test Connector connected to the Scan Tool.
What test do I run after installing the jumper wire?: Proceed with the KOEO Self-Test according to the instructions in the Scan Tool Owner's Manual.
What can I use as a ground point for the jumper wire?: Either the vehicle's battery negative post or a known good ground — a clean spot on the vehicle's metal frame.