For 1990-2009 cars

# SERVICE MANUAL UPDATE-SEC.8A CIRCUIT ID/COMPONENT LOCATION

#### SUBJECT: SERVICE INFORMATION MANUAL UPDATE - SECTION 8A ELECTRICAL DIAGNOSIS

Please update your Service Information Manuals with the following information: 1987 Eldorados and Sevilles:

- On pages 8A-88-1, "A-150-0, 2, 4, 6, 8, and 10 circuit 724 is PURPLE/YELLOW, not a flex circuit.

- On pages 8A-150-0, 2, 4, 6, 8, and 10 circuit 588 is BROWN, not a flex circuit.

- On pages 8A-150-4 and 8 circuit 8 is GREY, not a flex circuit.

1990 Eldorados and Sevilles:

- On pages 8A-88-1, 8A-150-0 and 2 circuit 724 is PURPLE/YELLOW, not a flex circuit.

- On pages 8A-150-0 and 2 circuit 588 is BROWN, not a flex circuit.

- On pages 8A-150-0 and 2 circuit 8 is GREY, not a flex circuit.

1988-1989 Broughams:

- On page 8A-110-10 connector C399 is located in the trunk, below the pack- age shelf, not under the rear seat.

1990 DeVilles and Fleetwoods:

- On page 8A-44-4 the location of the Electronic Brake Control Module (EBCM) is behind the center of the I/P, not below the ashtray, except on vehicles without SIR which have EBCM's located behind the left side of the instrument panel near the LH shroud.

- On page 8A-64-2 several component locations have changed. Please replace this page with the attached page 8A-64-2.

- On pages 8A-34-4, 5, and 8 some diagnosis steps have changed. Please replace these pages with the attached pages 8A-34-4, 5, and 8.

COMPONENT LOCATION Page-Figure A/C Compressor............. RH front of dash,...........201-4-B Control Relay on bracket

A/C Low................... Near RH fender,.............201-5-A Pressure Switch on A/C accumulator

Body Computer.............. RH side of I/P,.............201-11-A Module (BCM) behind glove box

Compressor Clutch...........RH front of engine,.........201-2-B on A/C compressor

Compressor Clutch...........Lower front of..............201-2-B Diode engine, in engine harness

Coolant Temperature.........Top center of...............201-4-C Sensor engine, behind distributor

Electronic Control..........Behind RH side..............201-12-B Module (ECM) of I/P, near shroud

Fuse Block..................LH side of I/P,..............201-5-B behind access door

Power Steering............ Lower rear of engine.........201-1-E Pressure Switch compartment, on steering box

Refrigerant High Engine compartment, Side Temperature near RH strut Sensor......................tower........................201-5-A

Refrigerant Low RH front of dash, Side Temperature on A/C line Sensor....................................................201-4-A

Relay Center................Behind RH side of.............201-17-A I/P, at RH shroud

Throttle Position.......... Top of engine,.................201-0-A Sensor (TPS) behind throttle body

C108 (1 cavity).............Lower LH side of engine compartment, in front of ELC Compressor Assembly............201-2-A

C200 (60 cavities)..........Behind LH side of..............201-14-A I/P, right of steer- ing column.

C210 (7 cavities)...........Behind LH side of I/P, taped to composite harness..............201-16-A

C225 (56 cavities)..........Behind RH side.................201-12-B of I/P

Gl00........................Engine compartment,............201-2-A ahead of LH wheelhouse.

G101........................RH side of engine,.............201-0-A on generator mount- ing bolt

S144........................Engine harness, on.............201-0-C RH side of rear valve cover

S201........................Composite harness,............ 201-16-A behind LH side of I/P

S218........................Composite harness,.............201-17-A behind RH side of I/P

S235........................Composite harness,.............201-8-B behind center of I/P

S250........................Composite harness,.............201-12-B behind RH side of I/P

S262........................Composite harness,.............201-8-B behind center of I/P

S293........................Engine harness,................201-12-B behind RH side of I/P

SYSTEM DIAGNOSIS - Refer to Section 1 C for diagnosis.

CIRCUIT OPERATION

The Compressor for the Air Conditioning System is belt-driven by the engine through the Compressor Clutch. The clutch allows the Compressor to be disengaged from the engine whenever air conditioning is not required.

The operation of the Compressor Clutch is controlled by the Electronic Control Module (ECM) by grounding the 366 circuit at connector C1, terminal C6. This energizes the A/C Compressor Control Relay and voltage is applied to the Compressor Clutch.

The Climate Control Panel (CCP) accepts input requests from the driver via the front panel push buttons. The input signals determine the operating mode for the Climate Control System and are sent to the Body Computer Module (BCM) over a data line (Circuit 718). If the BCM senses that cooling is required, it will signal the ECM to turn on the Compressor through a data line (Circuit 491).

The BCM cycles the Compressor on and off according to the temperature levels indicated by the A/C High Side and Low Side Temperature Inputs. Should the refrigerant level drop to a point where further operation would damage the Compressor, the A/C Low Pressure Switch opens and the BCM signals the ECM to stop compressor operation.

The ECM also receives inputs which affect operation of the Compressor. The inputs are Throttle Position, Coolant Temperature, Vehicle Speed and Power Steering Pressure.

CIRCUIT OPERATION

The Cruise Control System operates a mechanical linkage to the throttle by means of a Vacuum Motor. This is a diaphragm move by a vacuum applied to one side. A solenoid operated valve connects the Vacuum Motor to a Vacuum Tank. Another solenoid valve vents the vacuum to reduce the suction. The Electronic Control Module (ECM) controls the Vacuum Motor and the throttle by pulsing these solenoid valves on and off.

One input to the ECM is the vehicle speed. This input comes from the Vehicle Speed Sensor. If the actual speed signal is different from the speed that was set into and remembered by the ECM, the ECM generates pulses to change the vacuum and return the vehicle to the set speed. Other inputs to the Module are from the Cruise Control Switch and the Multi-Function Lever. A disconnect input to the ECM comes from a switch on the brake pedal. A sepa- rate vacuum shut-down of Cruise Control comes from the Cruise Control Vacuum Release Valve on the brake pedal.

Two outputs of the ECM operate the coils of the Vacuum Valve and the Vent Valve. Both Valves are located in the Cruise Control Servo. These valves move the throttle by means of the Vacuum Motor.

The Throttle Position Sensor in the throttle body senses the position and motion of the Vacuum Motor. It feeds back information to the ECM to provide smooth throttle changes while the vehicle is in Cruise Control.

If the ECM diagnostics detect a fault with the Vehicle Speed Sensor (Code E24) the Cruise Control System will be inhibited for the entire ignition cycle. The Cruise Control System will also be inhibited if:

1. Cruise Control is requested above 90 MPH,

2. The transaxle is shifted to PARK/NEUTRAL (Code E60)

3. There is a very rapid increase in RPM's (Code E66)

4. The difference between the vehicle's speed and the set speed is too high (Code E63)

5. A Cruise Switch is stuck closed or an ECM signal wire is shorted to volt- age when the system is enable (Code E67)

6. The ECM detects battery voltage above 16 volts or below 10 volts with en- gine running above 500 RPM (Code E16)

7. The acceleration is too high (Code E64)

8. A Cruise Control Servo Position Sensor is shorted to ground (Code E65)

9. The Cruise Control is on, the Brake is not depressed and the }Vent ECM output is HI when it should be LO, or vice-versa (Code E61)}Solenoid

10. The Cruise Control is on, the Brake is not depressed and the {Vent ECM output is HI when it should be LO, or vice-verse (Code E62)}Solenoid

11. A throttle angle greater than 20 degrees and the servo position sensor indicates a strokes greater than commanded (Code E68), or

12. The servo position sensor indicates that the servo is still engaged after Cruise Control has been disengaged (Code E99).

SYSTEM CHECK TABLE

ACTION NORMAL RESULT Put the Cruise Control Switch in the OFF position. Drive with care and accelerate to 50 mph. Put the Cruise Control Switch in the ON position ------------------------------------------------- Engage the system Cruise ENGAGED by momentarily Indicator lights pushing the Set/ when the button is Coast button and released and the releasing it when the system is engaged vehicle speed is at 50 mph ------------------------------------------------- Remove pressure The vehicle from the accelerator maintains speed of 50 mph ------------------------------------------------- Push the Resume/ The vehicle Accel button and accelerates at a hold controlled rate ------------------------------------------------- Release the Resume/ The vehicle is now Accel button to set at the new speed, engage system at a and vehicle cruise speed of maintains that approximately 55 speed mph ------------------------------------------------- Allow the vehicle to The vehicle slow to approximately accelerates at a 45 mph, using brakes controlled rate, and if desired, and resumes and maintains the previously set speed momentarily push of 55 mph the Resume/Accel button and then release -------------------------------------------------

Refer to System Diagnosis when a result is not normal.

#### SYSTEM DIAGNOSIS

Do the tests below if Cruise Control does not operate properly.

1. Start the engine and enter diagnostics.

- If no codes are displayed, go to step 2.

- If any codes are displayed or diagnostics cannot be entered, refer to the Self-Diagnostic System Check in Section 8D.

2. Start the engine and enter diagnostic mode. Do the actions shown in the Switch Tests table for each of the diagnostic displays listed. If the action is accepted (component is OK), the display will advance one step. If not, the display will advance after 10 seconds. After the last display those codes that did not pass win be displayed.

#### NOTE: If the Cruise ON/OFF Switch or Cruise Brake Switch has failed, the Switch Tests cannot be entered.

SWITCH TESTS Conditions:

- Engine running - ECM in Diagnostic Mode - Cruise ON/OFF Switch: ON - Fuel Data Center (FDC) displaying.7.0 ------------------------------------------------ Note: At this time hi and lo Diagnostic blower buttons can be used to Display increment to the next test or decrement to a previous test. ------------------------------------------------ E.7.0 Depress and release brake pedal ------------------------------------------------ E.7.1 Depress and release brake pedal ------------------------------------------------ E.7.2 Depress and release accelerator pedal ------------------------------------------------ E.7.3 Disconnect 5 way transaxle connector then reconnect ------------------------------------------------ E.7.5 Turn Cruise ON/OFF Switch OFF then ON ------------------------------------------------ E.7.6 Push and release the Cruise SET/COAST button ------------------------------------------------ E.7.7 Push and release the cruise RESUME/ACCEL switch ------------------------------------------------ E.7.8 Turn wheels from straight ahead to full right or left, then to straight ahead ------------------------------------------------

- If all switch tests pass, proceed to Cruise Servo test page 34-5. If any switch test fails, refer to the appropriate switch test trouble tree section 8D1.

#### Note: Either the VCC Brake Switch or Cruise Brake Switch will dise age the Cruise Control.

General Motors bulletins are intended for use by professional technicians, not a "do-it-yourselfer". They are written to inform those technicians of conditions that may occur on some vehicles, or to provide information that could assist in the proper service of a vehicle. Properly trained technicians have the equipment, tools, safety instructions and know-how to do a job properly and safely. If a condition is described, do not assume that the bulletin applies to your vehicle, or that your vehicle will have that condition. See a General Motors dealer servicing your brand of General Motors vehicle for information on whether your vehicle may benefit from the information.