Ccc Components Removal & Installation GMC Value Van P2500

Note. Most Computer Command Control (CCC) problems are the result of mechanical breakdowns, poor electrical connections, or damaged vacuum hoses. Before considering the CCC system as a possible cause of problems, check ignition high tension wires, fuel supply, electrical connections, and vacuum hoses. Failure to do so may result in lost diagnostic time.

STATIC CHARGE (VOLTS)

Servicing ECM Using 3M Anti-Static Mat. Scheme 1

ECM/MEM-CAL - 1986-91 MODELS WITH MEM-CAL

Note. To prevent damage to ECM, ignition must be off before disconnecting or reconnecting any ECM power source (i.e.; battery, ECM connectors, ECM fuse, jumper cables, etc.).

Note. The following steps are courtesy of general motors technical service bulletin no. T-91-95, june, 1991 & Technical Service Bulletin No. 91-6E-18, June, 1991

Problem

When installing a service replacement ECM, the use of incorrect MEM-CAL installation procedures may cause the ECM to fail before it can be installed in the vehicle. This condition may appear as if the ECM were defective when it was shipped to the dealership when, in fact, it was damaged while being installed. In addition, this condition may also occur when installing as "updated" service into the vehicle's original equipment ECM. Excessive vertical force may be generated in two ways

1. 1) Incorrect MEM-CAL installation procedure.
2. 2) Interference between MEM-CAL and cover.

Repair

To repair this condition use the following procedure: This procedure supersedes any instructions regarding MEM-CAL installation dated prior to September, 1990.

1. Inspect the MEM-CAL to determine if a cork spacer is glued to the top side of the MEM-CAL assemly. If so, remove it prior to installation.
2. Align small notches with matching notches in the ECM MEM-CAL socket.
3. VERY GENTLY press down on the ends of the MEM-CAL until the locking levers are rotated toward the sides of the MEM-CAL. NOTE: To avoid ECM damage, do not press on the ends of the MEM-CAL unit until the levers snap into place. DO NOT use any vertical force beyond the minimum required to engage the MEM-CAL into its socket.
4. While continuing light pressure on the ends of the MEM-CAL, use your index fingers to press the locking levers inward until they are snapped into place. Listen for click.
5. Install MEM-CAL cover and install ECM in vehicle.

Note. If diagnostic procedures require replacement of ECM, ensure ECM and PROM part numbers are correct. Service ECM DOES NOT contain a PROM. Old PROM must be installed in service ECM. Part number verification is critical for proper vehicle operation.

1. Remove ECM from vehicle. Remove access cover. Note location of reference notch in PROM and ECM for reassembly reference. Engage end of PROM carrier with hook end of rocker-type PROM removal tool. Press on vertical bar end of tool and rock engaged end of PROM carrier up as far as possible.
2. Engage opposite end of PROM carrier in the same manner and rock this end up as far as possible. Repeat process until PROM carrier and PROM are free of PROM socket. PROM carrier and PROM should lift off of PROM socket easily.

Note. PROM carrier should ONLY be removed with special PROM removal tool. Use of any other method may damage PROM or PROM socket.

1. Check that new PROM has same service number as the one being replaced. Place new PROM and carrier in ECM. Press on PROM carrier until PROM is firmly seated in ECM. Make sure that reference notch in ECM and PROM are properly aligned.
2. Install PROM access cover on ECM and install ECM in vehicle. Start engine and ground diagnostic test lead. Code 12 should flash at least 4 times, with no other codes stored. This confirms proper PROM installation.
3. If Code 51 is stored, or if "SERVICE ENGINE SOON" light stays on constantly, PROM is not fully seated in ECM, is installed backwards, has bent pins or is defective. If pins are bent and crack when straightened, PROM must be replaced. If PROM is installed backwards or is defective, it must be replaced.

Replacing PROM in Electronic Control Module Always use PROM removal tool when replacing PROM. Scheme 2

Disconnect negative battery cable at battery. Raise vehicle, if required. Disconnect electrical connector from oxygen sensor. Carefully remove O2 sensor from exhaust pipe.

Note. O2 sensor may be difficult to remove when engine temperature is below 120°F (49°C). Excessive removal force may damage threads in exhaust manifold or pipe.

1. Whenever an O2 sensor is removed, its threads must be coated with anti-seize compound before it is installed. New sensors will already have this compound applied to threads.
2. Install O2 sensor in exhaust pipe and tighten to 30 ft. lbs. (41 N.m). Reconnect electrical connector to sensor. Lower vehicle from hoist. Reconnect negative battery cable to battery.

Remove air cleaner assembly. Disconnect electrical connector from TPS. Remove 2 TPS attaching screws, lockwashers, and retainers. Remove TPS.

1. With throttle valve in normal closed idle position, install TPS on throttle body. Make sure that TPS lever is located above tang on throttle actuator lever.
2. Apply thread locking compound to TPS screws. Install TPS screws, lock washers, and retainers. Connect electrical lead and install air cleaner.

1. Disconnect M/C solenoid and TPS electrical connectors. Remove choke lever from end of choke shaft by removing retaining screw. Rotate upper choke lever to remove lever from choke rod.
2. Remove choke link from lower lever inside float bowl casting. Remove rod by holding lower lever outward with small screwdriver and twisting rod counterclockwise. Remove retainer from pump link, and remove link from lever. DO NOT remove pump lever from air horn.
3. Disconnect front vacuum break hose from tube on float bowl. Remove secondary metering rod retaining screw. Lift holder with metering rods straight up and out of air horn.
4. Remove air horn-to-bowl screws; then remove the 2 countersunk attaching screws located next to venturi. Remove carburetor air horn assembly up and off of float bowl. Leave gasket on float bowl.
5. Remove solenoid adjusting screw and rich limit stop using Wrench (J-28696-10). Remove solenoid/metering rod plunger by lifting it straight up. Remove air horn gasket by lifting it from locating pins on float bowl. Discard gasket.
6. Remove float bowl insert. Remove metering rods and spring. Push up from bottom on TPS electrical connector and remove TPS and connector assembly from bowl.

Scheme 3

1. Install TPS and connector assembly in float bowl by aligning groove in electrical connector with slot in float bowl casting. Push down on connector and sensor assembly so that connector and wires are located below bowl casting surface.
2. Install pump plunger spring and pump plunger. Install TPS plunger by pushing up through seal in air horn. While holding pump plunger down, position new air horn gasket over pump plunger stem and over 2 locating pins on float bowl.
3. Carefully lower air horn assembly onto float bowl while positioning TPS adjustment lever over TPS, and guiding pump plunger stem through seal in air horn casting. To ease installation, insert a thin screwdriver between air horn gasket and float bowl to raise TPS adjustment lever, positioning it over sensor.
4. Install air horn screws, lockwashers, and 2 countersunk screws. Tighten all screws evenly and securely, following air horn screw tightening sequence. (Scheme 3) (Scheme 3): Air Horn Screw Tightening Sequence
5. Install pump link to pump lever and insert retainer pin. Install secondary metering rods on metering rod holder (upper ends of rods point toward each other).
6. Carefully lower rods into air horn and place holder onto air valve cam follower. Install retaining screw. Work air valves up and down to verify that they move freely and without binding.
7. Install choke rod into lower choke lever inside bowl cavity. Install choke rod into upper choke lever, and position lever on end of choke shaft. Make sure flats on end of shaft align with flats in lever. Install attaching screw and tighten securely.
8. Install front vacuum break and bracket assembly on air horn, using two attaching screws. Connect M/C solenoid and TPS electrical connectors. Check and adjust TPS voltage. See ADJUSTMENT.

Adjustment

1. Connect digital voltmeter between center "B" terminal and bottom "C" terminal of TPS connector. Read TPS voltage under these conditions: Ignition switch on, engine off. Disconnect electrical connector from idle solenoid (plunger retracted). Throttle lever against idle speed screw. TPS adjustment is required only if voltage readings are not within 0.24-0.26 volts for 4.3L engine, manual transmission equipped models; or 0.30-0.32 volts for all automatic transmission equipped models.
2. If adjustment is required, remove tamper-resistant plug covering TPS adjustment screw. Using a 5/64" bit, drill a 1/16" to 1/8" deep hole in plug. Use care in drilling to prevent damage to TPS adjustment screw head.
3. Start a No. 8, 1/2" long self-tapping screw in drilled hole, turning screw in only enough to ensure good thread engagement in hole. Placing a wide-blade screwdriver between screw head and air horn casting, pry against screw head to remove plug. Discard plug.
4. Using Wrench (J-28696 ), adjust TPS screw to obtain correct voltage. After adjustment, install new tamper-resistant plug (supplied in service kits) in air horn. Drive plug into place until flush with raised pump lever boss on casting. Clear trouble code memory after adjustment.

Removal of sensors, switches, and solenoids is accomplished by disconnecting the electrical and/or vacuum connectors and removing or detaching the component. To install, reverse removal procedure.

Replace driver only if diagnosis has determined that it has failed. The driver is inside a container, and taped to harness near ECM. Open container and replace driver as required.

ECM Terminal ID & Voltage Values (2.5L Engine). Scheme 4

ECM Terminal ID & Voltage Values (2.8L Engine). Scheme 5

ECM Terminal ID & Voltage Values (4.3L TBI Engine). Scheme 6

ECM Terminal ID & Voltage Values (4.3L Carbureted Engine). Scheme 7

ECM Terminal ID & Voltage Values (5.0L & 5.7L Engines). Scheme 8

Wiring Diagram (2.5L TBI Engine). Scheme 9

Wiring Diagram (2.8L TBI Engine). Scheme 10

Wiring Diagram (4.3L TBI Engine). Scheme 11

Wiring Diagram (4.3L Carbureted, 5.0L & 5.7L Engines). Scheme 12