Speed Control System: Other Mercury Montego III

Possible Causes

1. parking brake switch circuitry
2. speed control switch
3. digital transmission range (TR) sensor
4. vehicle speed signal
5. PCM

Scheme 8

1. A1 CHECK FOR DTCs Review the recorded DTCs from the powertrain control module (PCM) self-test. Are any DTCs recorded? Yes : REFER to the «POWERTRAIN CONTROL MODULE DIAGNOSTIC TROUBLE CODE INDEX»(ref-233055-S00475148842006052400000) . No : GO to A2.
2. A2 CHECK THE SPEED CONTROL SWITCH Disconnect: PCM C175b. Measure the resistance between the PCM C175b-19, circuit 848 (DG/OG), harness side and the PCM C175b-30, circuit 151 (LB/BK), harness side while pressing the speed control switch buttons as follows: SPEED CONTROL SWITCH RESISTANCE REFERENCE Speed Control Switch Resistance Value OFF Less than 5 ohms CANCEL 110 - 130 ohms SET- 276 - 324 ohms SET+ 552 - 648 ohms RESUME 1,021 - 1,199 ohms ON 1,941 - 2,278 ohms No switch pressed 3,965 - 4,655 ohms Are the speed control switch resistance values OK? Yes : GO to A3. No : INSTALL a new speed control switch. REFER to «SPEED CONTROL SWITCH»(ref-233055-S07676227032006052400000) . CLEAR the DTCs. REPEAT the self-test.
3. A3 MONITOR THE TRANSMISSION RANGE PID Connect: PCM C175b. Key in ON position. Enter the following diagnostic mode on the diagnostic tool: PID Data Monitor and Record. Monitor the transmission range PID. Select DRIVE. Does the PID value agree with the transmission range selector lever position? Yes : GO to A4. No : REFER to «AUTOMATIC TRANSAXLE/TRANSMISSION - CVT»(ref-233028) or «AUTOMATIC TRANSAXLE - 6 SPEED»(ref-233010) .
4. A4 CHECK THE PARKING BRAKE WARNING INDICATOR Key in ON position. While observing the parking brake warning indicator, apply and release the parking brake. Does the parking brake warning indicator operate correctly? Yes : GO to A5. No : REFER to «INSTRUMENT CLUSTER»(ref-233031) to diagnose the parking brake warning indicator.
5. A5 CHECK THE VEHICLE SPEED NOTE: This step may require an assistant. Enter the following diagnostic mode on the diagnostic tool: Anti-lock Brake System (ABS) Wheel Speed PID. Monitor and record the ABS module wheel speed PID while driving the vehicle at 48 km/h (30 mph) as indicated on the speedometer. Enter the following diagnostic mode on the diagnostic tool: PCM Vehicle Speed PID. Monitor and record the PCM vehicle speed PID while driving the vehicle at 48 km/h (30 mph). Does the speed indicated by the ABS module wheel speed PID match the PCM vehicle speed PID? Yes : GO to A6. No : REFER to the «INTRODUCTION - GASOLINE»(ref-229953) article to diagnose the output shaft sensor (OSS) signal.
6. A6 CHECK FOR CORRECT PCM OPERATION Disconnect all the PCM connectors. Check for: corrosion pushed-out pins Connect all the PCM connectors and make sure they are seated correctly. Operate the system and verify the concern is still present. Is the concern still present? Yes : INSTALL a new PCM. REFER to «ELECTRONIC ENGINE CONTROLS»(ref-233038) . CLEAR the DTCs. REPEAT the self-test. No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.

1. circuit 307 (BK/YE) open or short to voltage
2. circuit 1140 (VT) open
3. speed control deactivator switch
4. PCM

Scheme 9

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Scheme 12

1. B1 CHECK THE STOPLAMPS Verify the stoplamps operate correctly. Do the stop lamps operate correctly? Yes : GO to B2. No : REFER to «EXTERIOR LIGHTING»(ref-233037) to continue diagnosis of the stop lamps.
2. B2 CHECK THE SPEED CONTROL DEACTIVATOR SWITCH FOR CORRECT OPERATION Key in OFF position. Disconnect: PCM C175b. Key in ON position. While firmly applying and releasing the brake pedal, measure the voltage between the PCM C175b-7, circuit 307 (BK/YE), harness side and ground. Is the voltage greater than 10 volts with the brake pedal released and 0 volts with the brake pedal firmly applied? Yes : GO to B6 . No : GO to B3.
3. B3 CHECK CIRCUIT 1140 (VT) FOR AN OPEN Key in OFF position. Disconnect: Speed Control Deactivator Switch C2227. Key in ON position. Measure the voltage between the speed control deactivator switch C2227-2, circuit 1140 (VT), harness side and ground. Is the voltage greater than 10 volts? Yes : GO to B4. No : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
4. B4 CHECK CIRCUIT 307 (BK/YE) FOR A SHORT TO POWER Measure the voltage between the speed control deactivator switch C2227-1, circuit 307 (BK/YE), harness side and ground. Is any voltage present? Yes : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test. No : GO to B5.
5. B5 CHECK CIRCUIT 307 (BK/YE) FOR AN OPEN Key in OFF position. Measure the resistance between the speed control deactivator switch C2227-1, circuit 307 (BK/YE), harness side and the PCM C175b-7, circuit 307 (BK/YE), harness side. Is the resistance less than 5 ohms? Yes : INSTALL a new speed control deactivator switch. REFER to «SPEED CONTROL DEACTIVATOR SWITCH»(ref-233055-S11980443962006052400000) . CLEAR the DTCs. REPEAT the self-test. No : REPAIR the circuit. CLEAR the DTCs. REPEAT the self-test.
6. B6 CHECK FOR CORRECT PCM OPERATION Disconnect all the PCM connectors. Check for: corrosion pushed-out pins Connect all the PCM connectors and make sure they are seated correctly. Operate the system and verify the concern is still present. Is the concern still present? Yes : INSTALL a new PCM. REFER to «ELECTRONIC ENGINE CONTROLS»(ref-233038) . No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. CLEAR the DTCs. REPEAT the self-test.

1. circuit 151 (LB/BK) open, short to voltage, or short to ground
2. circuit 848 (DG/OG) open short to voltage
3. clockspring
4. speed control switch
5. PCM

Scheme 13

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Scheme 17

1. C1 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR A SHORT TO VOLTAGE Key in OFF position. Disconnect: PCM C175b. Key in ON position. Turn the parking lamps on. Measure the voltage between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground. Is any voltage present? Yes : TURN the parking lamps off. GO to C2. No : TURN the parking lamps off. GO to C4 .
2. C2 CHECK CIRCUITS 151 (LB/BK) AND 848 (DG/OG) FOR A SHORT TO VOLTAGE Key in OFF position. Disconnect: Clockspring C2274a. Key in ON position. Turn the parking lamps on. Measure the voltage between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground. Is any voltage present? Yes : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test. No : TURN the parking lamps off. GO to C3.
3. C3 CHECK THE CLOCKSPRING FOR A SHORT TO VOLTAGE Key in OFF position. Connect: Clockspring C2274a. Remove the driver air bag module. Refer to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . Connect the restraint system diagnostic tool (418-F403) to the upper clockspring air bag connector. Disconnect: Upper Clockspring. WARNING: Make sure there is no one inside the vehicle and that there is nothing blocking the or set in front of any air bag module when the battery is connected. Failure to follow these instructions may result in personal injury. Connect the battery. Key in ON position. Turn the parking lamps on. Measure the voltage between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground. Is any voltage present? Yes : INSTALL a new clockspring. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . DISCONNECT the battery. INSTALL the driver air bag module. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . CLEAR the DTCs. REPEAT the self-test. No : INSTALL a new speed control switch. REFER to «SPEED CONTROL SWITCH»(ref-233055-S07676227032006052400000) . DISCONNECT the battery. INSTALL the driver air bag module. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . CLEAR the DTCs. REPEAT the self-test.
4. C4 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR A SHORT TO GROUND Key in OFF position. Measure the resistance between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground. Are the resistances greater than 10,000 ohms? Yes : GO to C7 . No : GO to C5.
5. C5 CHECK THE CLOCKSPRING FOR A SHORT TO GROUND Remove the driver air bag module. Refer to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . Disconnect: Upper Clockspring. Measure the resistance between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground. Are the resistances greater than 10,000 ohms? Yes : INSTALL a new speed control switch. REFER to «SPEED CONTROL SWITCH»(ref-233055-S07676227032006052400000) . INSTALL the driver air bag module. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . CLEAR the DTCs. REPEAT the self-test. No : GO to C6.
6. C6 CHECK CIRCUITS 151 (LB/BK) AND 848 (DG/OG) FOR A SHORT TO GROUND Disconnect: Clockspring C2274a. Measure the resistance between the PCM C175b-30, circuit 151 (LB/BK), harness side and ground; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and ground. Are the resistances greater than 10,000 ohms? Yes : INSTALL a new clockspring. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . INSTALL the driver air bag module. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . CLEAR the DTCs. REPEAT the self-test. No : REPAIR the circuit in question. INSTALL the driver air bag module. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . CLEAR the DTCs. REPEAT the self-test.
7. C7 CHECK THE SPEED CONTROL SWITCH CIRCUITRY FOR AN OPEN Disconnect: Clockspring C2274a. Measure the resistance between the PCM C175b-30, circuit 151 (LB/BK), harness side and the clockspring C2274a-5, circuit 151 (LB/BK), harness side; and between the PCM C175b-19, circuit 848 (DG/OG), harness side and the clockspring C2274a-4, circuit 848 (DG/OG), harness side. Is the resistance less than 5 ohms? Yes : GO to C8. No : REPAIR the circuit in question. CLEAR the DTCs. REPEAT the self-test.
8. C8 CHECK THE CLOCKSPRING Remove the driver air bag module. Refer to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . Disconnect: Upper Clockspring. Measure the resistance between the upper clockspring pin 3, component side and the clockspring pin 5, component side; and between the upper clockspring pin 2, component side and the clockspring pin 4, component side. Are the resistances less than 5 ohms? Yes : GO to C9. No : INSTALL a new clockspring. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . INSTALL the driver air bag module. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . CLEAR the DTCs. REPEAT the self-test.
9. C9 CHECK THE SPEED CONTROL SWITCH Measure the resistance between the upper clockspring pin 2, harness side and the upper clockspring pin 3, harness side. Is the resistance between 3,965 and 4,655 ohms? Yes : GO to C10. No : INSTALL new speed control switch. REFER to «SPEED CONTROL SWITCH»(ref-233055-S07676227032006052400000) . INSTALL the driver air bag module. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . CLEAR the DTCs. REPEAT the self-test.
10. C10 CHECK FOR CORRECT PCM OPERATION Disconnect all the PCM connectors. Check for: corrosion pushed-out pins Connect all the PCM connectors and make sure they are seated correctly. Operate the system and verify the concern is still present. Is the concern still present? Yes : INSTALL a new PCM. REFER to «ELECTRONIC ENGINE CONTROLS»(ref-233038) . INSTALL the driver air bag module. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . TEST the system for normal operation. No : The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector. INSTALL the driver air bag. REFER to «SUPPLEMENTAL RESTRAINT SYSTEM»(ref-233039) . CLEAR the DTCs. REPEAT the self-test.

Scheme 18