Remove ISO relay. Using 2 jumper wires, connect positive battery terminal to relay terminal No. 85 and negative battery terminal to relay terminal No. 86. See Fig 1 . Continuity should exist between relay terminals No. 30 and No. 87 only. If as specified, go to next step. If continuity exists between relay terminals No. 30 and No. 87a, replace ISO relay.
Disconnect jumper wires. Check for continuity between relay terminal No. 85 and all other terminals. Continuity should exist between terminals No. 85 and No. 86 only. If as specified, go to next step. If continuity exists between terminal No. 85 and any other terminal except terminal No. 86, replace ISO relay.
Check for continuity between terminal No. 30 and all other terminals. Continuity should exist between terminals No. 30 and No. 87a only. If as specified, go to next step. If continuity exists between terminal No. 30 and any other terminal except terminal No. 87a, replace ISO relay.

Fig 1: Identifying ISO Relay Terminals

Courtesy of FORD MOTOR CO.

When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.

• Brakes feel soft, pull hard to one side, or make grinding noises.

• The engine overheats, stalls repeatedly, or misfires under load.

• You are missing required tools, torque specs, or safe lifting equipment.

• You are not confident in the next step or safety outcome.

Safety Warning

ISO Relay Test