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 MANUALSCHEVROLET1999SUBURBAN C2500, 6.5 FREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMENGINE CONTROL SYSTEM - TESTS W/CODES - DTC P1537-U1193DTC P1635DTC P1635: 5-VOLT REFERENCE ERROR (1.9L SATURN)DIAGNOSTIC PROCEDURES
1999 Chevrolet Suburban C2500, 6.5 F
Diagnostic Procedures
1999 Chevrolet Suburban C2500, 6.5 FSECTION Diagnostic Procedures
- Install scan tool. Turn ignition on. Using scan tool, monitor TP sensor, MAP and EGR voltages. If they all read less than.24 volt, go to next step. If MAP voltage is greater than 5.1 volts, go to step 4. If MAP voltage is not greater than 5.1 volts, problem is intermittent. See DIAGNOSTIC AIDS .
- Turn ignition off. Disconnect PCM harness connector J2. Using a test light connect to battery voltage, probe PCM harness connector terminals J2B04 and J2B05. If test light illuminates, go to next step. If test light does not illuminate, replace PCM.
- Disconnect MAP, EGR, and TP sensor one at a time. If test light goes out when disconnecting a component, replace that component. If test light stays on, repair short to ground in affected circuit.
- Turn ignition off. Disconnect PCM harness connector J2. Turn ignition on. Check voltage on PCM harness connector terminals J2B04 and J2B05. If voltage is present, repair short to voltage in affected circuits. If voltage is not present, replace PCM.
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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.