Computers and Control Systems: Symptom Related Diagnostic Procedures C Charts. Part 1 of 6. Chart C-1 (1 Of 6)

1993 Cadillac DeVille V8-300 4.9L Page 1 Computers and Control Systems: Symptom Related Diagnostic Procedures C Charts Part 1 of 6 Chart C-1 (1 Of 6)

1993 Cadillac DeVille V8-300 4.9L Page 2 Wiring Diagram. DESCRIPTION: The BCM supplies the FDC and ECC with certain information. Through CKT 719, the BCM sends data to the FDC. Through CKT 705, the BCM supplies the FDC and ECC with a 5 volt reference. Through CKT 751, The BCM supplies a reference ground. A clock signal is provided to the FDC and ECC over CKT 713. The BCM supplies a 16 volt source to the ECC and the FDC through CKT 716. Through CKT 718, the BCM sends data to the ECC. NOTES ON FAULT TREE: 1. A "C" displayed on one or both panels indicates a loss of the clock signal to the affected panel. 2. A "D" displayed on either panel indicates a loss of the data signal to the affected panel. 3. If one panel is affected, only branches of the critical circuits to that panel require investigation. 4. If both panels are affected, several circuits then require investigation. If depressing the off button on the ECC does not result in the blower turning off, then the panels are not in communication with the BCM. This could be caused by a loss of 5 volts or ground to the panels. If the blower turns off, all remaining critical circuits must be checked. Part 2 of 6 (Chart C-1A)

1993 Cadillac DeVille V8-300 4.9L Page 3 Diagnostic Chart.

1993 Cadillac DeVille V8-300 4.9L Page 4 Wiring Diagram. DESCRIPTION: The BCM supplies the FDC and ECC with certain information. Through CKT 719, the BCM sends data to the FDC. Through CKT 705, the BCM supplies the FDC and ECC with a 5 volt reference. Through CKT 751, The BCM supplies a reference ground. A clock signal is provided to the FDC and ECC over CKT 713. The BCM supplies a 16 volt source to the ECC and the FDC through CKT 716. Through CKT 718, the BCM sends data to the ECC. Part 3 of 6 (Chart C-1B)

1993 Cadillac DeVille V8-300 4.9L Page 5 Chart C-1b (3 Of 6)

1993 Cadillac DeVille V8-300 4.9L Page 6 Wiring Diagram. DESCRIPTION: The BCM supplies the FDC and ECC with certain information. Through CKT 719, the BCM sends data to the FDC. Through CKT 705, the BCM supplies the FDC and ECC with a 5 volt reference. Through CKT 751, The BCM supplies a reference ground. A clock signal is provided to the FDC and ECC over CKT 713. The BCM supplies a 16 volt source to the ECC and the FDC through CKT 716. Through CKT 718, the BCM sends data to the ECC. Part 4 of 6 (Chart C-1C)

1993 Cadillac DeVille V8-300 4.9L Page 7 Chart C-1c

1993 Cadillac DeVille V8-300 4.9L Page 8 Wiring Diagram. DESCRIPTION: The BCM supplies the FDC and ECC with certain information. Through CKT 719, the BCM sends data to the FDC. Through CKT 705, the BCM supplies the FDC and ECC with a 5 volt reference. Through CKT 751, The BCM supplies a reference ground. A clock signal is provided to the FDC and ECC over CKT 713. The BCM supplies a 16 volt source to the ECC and the FDC through CKT 716. Through CKT 718, the BCM sends data to the ECC. Part 5 of 6 (Chart C-1D)

1993 Cadillac DeVille V8-300 4.9L Page 9 Chart C-1d

1993 Cadillac DeVille V8-300 4.9L Page 10 Wiring Diagram. DESCRIPTION: The BCM supplies the FDC and ECC with certain information. Through CKT 719, the BCM sends data to the FDC. Through CKT 705, the BCM supplies the FDC and ECC with a 5 volt reference. Through CKT 751, The BCM supplies a reference ground. A clock signal is provided to the FDC and ECC over CKT 713. The BCM supplies a 16 volt source to the ECC and the FDC through CKT 716. Through CKT 718, the BCM sends data to the ECC. Part 6 of 6 (Chart C-1E)

1993 Cadillac DeVille V8-300 4.9L Page 11 Chart C-1e

1993 Cadillac DeVille V8-300 4.9L Page 12 Wiring Diagram. DESCRIPTION: The BCM supplies the FDC and ECC with certain information. Through CKT 719, the BCM sends data to the FDC. Through CKT 705, the BCM supplies the FDC and ECC with a 5 volt reference. Through CKT 751, The BCM supplies a reference ground. A clock signal is provided to the FDC and ECC over CKT 713. The BCM supplies a 16 volt source to the ECC and the FDC through CKT 716. Through CKT 718, the BCM sends data to the ECC.

1993 Cadillac DeVille V8-300 4.9L Page 13 Fig. 8 ECM Replacement Check Chart C-3 Canister Purge Check

1993 Cadillac DeVille V8-300 4.9L Page 14 Canister Purge Diagnosis

1993 Cadillac DeVille V8-300 4.9L Page 15 Wiring Diagram CIRCUIT DESCRIPTION The canister purge solenoid receives 12 volts from the 10 amp number 3 fuse on the underhood relay panel through circuit 639. The PCM energizes the canister purge solenoid by grounding pin E7 (circuit 428). When the solenoid is energized it allows the canister to purge. The canister is commanded to purge when: ^ ^ ^ ^ ^ Coolant is above 80 C. Closed loop has been achieved for at least 30 seconds. Throttle switch is open. Vehicle speed sensor is greater than 10 mph. Engine speed (RPM) ^ above a threshold. OR Code E013, E044, or E045 are present. FUNCTIONAL TEST 1. Disconnect the hose leading from the Tank Pressure Control Valve, (TPCV) to the lower port of the charcoal canister at the canister end. 2. Attach a hose to the fuel tank port of the TPCV and attempt to blow through it. Little or no air should pass through the TPCV. 3. With a hand vacuum pump, apply vacuum (15" Hg. or 51 kpa) through the TPCV upper tube (manifold vacuum supply port). If the diaphragm does not hold 10" of vacuum for at least 10 seconds, the diaphragm is leaking, and the TPCV must be replaced. If the diaphragm holds vacuum, try to blow through the hose connected to the lower tube while vacuum is still being applied. An increased flow of air should be observed. If not, replace the TPCV. 4. Attach a hose to the lower port of the canister and attempt to blow through it. Air should pass into the canister. If not, replace the canister. 5. Disconnect the canister purge solenoid electrical connector, attach a hose to the upper port of the canister, and attempt to blow through it. Air should not pass into the canister. If air passes, replace the purge solenoid. 6. Measure the resistance of the purge solenoid. Resistance should be greater than 20 ohms and less than 100 ohms. If the solenoid resistance is not in this range, replace the solenoid.

1993 Cadillac DeVille V8-300 4.9L Page 16 7. Reconnect all purge hoses and the solenoid electrical connector. Chart C-4 HEI System Check HEI Performance Test

1993 Cadillac DeVille V8-300 4.9L Page 17 HEI Wiring Diagram

1993 Cadillac DeVille V8-300 4.9L Page 18 Chart C-4A DESCRIPTION: The HEI performance test checks the operation of the control circuits and ground plane of the module. CKT 453 forms the ground plane for the module. High resistance in this circuit can cause an interruption in the transmission of the signal. The module is dependant on the pick up coil to generate the alternating current signal that it processes into a square wave signal sent to the PCM. If the pick up coil fails to generate a voltage signal the module cannot produce a reference signal to the PCM. Attention should be paid to the pick up coil leads. An intermittent open in the pick up coil circuit can cause no start and stall conditions.

1993 Cadillac DeVille V8-300 4.9L Page 19 NOTES ON FAULT TREE: 1. Use essential tool J35616, or equivalent, to make necessary jumpers. 2. Manipulate the green and white leads of the pick up coil when checking with the Ohmmeter. 3. Check the ground at the generator and the grounding screw at the harness block. Chart C-7 Exhaust Gas Recirculation (EGR) System Check

1993 Cadillac DeVille V8-300 4.9L Page 20 EGR System Diagnostic Chart

1993 Cadillac DeVille V8-300 4.9L Page 21 Wiring Diagram TEST DESCRIPTION This engine uses a positive backpressure EGR valve which limits EGR flow with low exhaust backpressure (idle, decel, etc.). It is very important that shop exhaust tubes which decrease backpressure (pull air through) are not hooked to the vehicle when diagnosing the EGR system. ^ ^ Check 10 amp fuse (#5) in underhood relay center. Measure EGR solenoid resistance. Should be 20 to 100 ohms. VACUUM TEST 1. Connect a vacuum gauge to the source side of the EGR solenoid. Start the engine, manifold vacuum should be present. If it is not, repair leaks or obstruction between the EGR solenoid and throttle body. 2. Connect a vacuum gauge to the EGR valve vacuum supply. There should be no vacuum with the engine idling. If there is, follow chart C-7 above. 3. With the gauge hooked to the EGR valve vacuum supply, disconnect the EGR solenoid connector. There should be more than 15 inches of vacuum available. If not, repair leak or obstruction in EGR valve vacuum hose. NOTES ON INTERMITTENTS ^ ^ Check vacuum supply hoses for leaks, restrictions, and obstructions. Clean out or replace as necessary. Check intake manifold passages for any obstructions that would prevent exhaust gases from passing through.