Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSMAZDA1991NAVAJO LX, AUTOMATICREPAIR AND DIAGNOSISACCESSORIES & EQUIPMENTCRUISE CONTROL SYSTEMSCOMPONENT TESTINGSERVO TEST
1991 Mazda Navajo LX, Automatic
Servo Test
1991 Mazda Navajo LX, AutomaticSECTION Servo Test
- Unplug 8-pin connector at amplifier. Amplifier is located above glove box, behind dash. Measure resistance at specified wires on harness connector. See SERVO RESISTANCE
.SERVO RESISTANCE
Circuit No. (Wire Color) Ohms 144 (Orange/Yellow) - 145 (Gray/Black) 40-70 144 (Orange/Yellow) - 146 (White/Pink) 100-150 147 (Purple/Blue) - 149 (Brown/Green) 35,000-70,000 147 (Purple/Blue) - 148 (Yellow/Red) 15,000-35,000 148 (Yellow/Red) - 149 (Brown/Green) 15,000-35,000 NOTE: Resistance between circuits No. 147 and 148 should be nearly the same as resistance between circuits No. 148 and 149. If the difference is more than 5 k/ohms and vehicle has a surging problem, perform step 2). If resistances are okay, go to step 3). - If resistances are not correct, unplug 6-pin connector at servo. Ensure terminals are clean. Measure resistances at connector. See SERVO RESISTANCE
. If resistance is correct, check wiring harness and repair as necessary. If resistance is incorrect, replace servo and retest.CAUTION: If Orange/Yellow wire is shorted to either White/Pink wire or Gray/Black wire, damage to amplifier may occur.
- Disconnect servo. Start engine. Ensure vacuum to servo is at least 2.5 in. Hg. Connect circuit No. 144 (Orange/Yellow wire) of servo to positive battery terminal. Connect circuit No. 146 (White/Pink wire) of servo to ground. Momentarily connect circuit No. 145 (Gray/Black wire) of servo to ground.
- Servo throttle actuator arm should pull in and engine speed should increase. The throttle should hold in that position or slowly release. When circuit No. 146 (White/Pink wire) is removed from ground, servo should release. Replace servo if it fails test.
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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.