Test D8 - Turbo Boost

NOTE: Perform this test when Service Code 81 is displayed during QUICK TESTS or when directed here by other test procedures.

Fig 1: Turbo Boost Circuit

Output State Test: Enter OUTPUT STATE CHECK; see OUTPUT STATE CHECK under QUICK TEST DIAGNOSTIC AIDS . Use only DVOM, not diagnostic tester, for this step. Turn key off and wait 10 seconds. Set DVOM on 20-volt scale. Connect DVOM negative test lead to STO at SELF-TEST connector and positive test lead to positive battery terminal. Install a jumper wire between STI and signal return at SELF-TEST connector. Perform KEY ON/ENGINE OFF (KOEO) SELF-TEST until end of CONTINUOUS SELF-TEST codes (DVOM reads less than one volt). Depress and release throttle while watching DVOM reading. If reading did not change to a high voltage, depress throttle to WOT position and release. If STO voltage does not go to high reading, go to TEST D16 , step 1). Leave test equipment hooked up. If reading changes to high voltage, remain in OUTPUT STATE CHECK and go to next step.
Checking Boost Output Electrical Operation: With KOEO, set DVOM on 20-volt scale. Connect DVOM positive test lead to VPWR circuit at boost solenoid connector and negative test lead to boost output on boost solenoid connector. Depress and release throttle several times while reading DVOM. If boost solenoid does not cycle, remove jumper wire and go to step 4). If boost solenoid cycles, go to next step.
Checking Boost Solenoid Function: Remain in OUTPUT STATE CHECK. Disconnect turbo boost control solenoid vacuum hose at turbocharger inlet end. Attach vacuum pump to hose. Depress throttle once to cycle solenoid to closed position. Apply vacuum to solenoid, then depress throttle to cycle solenoid to open position and release vacuum. If solenoid does not hold and release vacuum properly, replace solenoid and repeat QUICK TEST . If solenoid works correctly, EEC system is okay. Check turbocharger boost system.
Check Voltage of VPWR Circuit: Turn key off and wait 10 seconds. Disconnect boost solenoid connector. With DVOM on 20-volt scale, measure voltage between VPWR circuit of boost solenoid at vehicle harness and battery negative terminal. If reading is less than 10.5 volts, repair wiring circuit and rerun QUICK TEST . If voltage is more than 10.5 volts, go to next step.
Measuring Boost Solenoid Resistance: With KOEO, disconnect boost solenoid and set DVOM on 200-ohm scale. Measure solenoid resistance. If resistance is 65-110 ohms, go to next step. If resistance is not within specification, replace solenoid and rerun QUICK TEST .
Checking Continuity of Boost Circuit: Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion or loose wires. Repair if necessary. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Measure resistance between Test Pin No. 31 and boost circuit at harness connector. If reading is 5 ohms or more, repair open and repeat QUICK TEST . If reading is less than 5 ohms, go to next step.
Checking For Short to Ground: Turn key off and wait 10 seconds. Leave breakout box installed and ECA disconnected. Disconnect boost solenoid and set DVOM on 200K-ohm scale. Measure resistance between Test Pin No. 31 and Test Pins No. 40, 46, and 60. If any reading is less than 10K ohms, repair short to ground and repeat QUICK TEST . If all readings are 10K ohms or more, go to next step.
Checking For Short to Power: Turn key off and wait 10 seconds. Leave breakout box installed, ECA disconnected, and DVOM on 200K-ohm scale. With boost solenoid disconnected, measure resistance between Test Pin No. 31 and Test Pins No. 37 and 57. If any reading is less than 10K ohms, repair short to power and repeat QUICK TEST . If symptom is still present, replace ECA. If all readings are 10K ohms or more, replace ECA and repeat QUICK TEST.