| CAUTION | When certain materials rub together, a transfer of electrons from one material to another may occur under special conditions. This results in an electrostatic charge (static electricity) being built up in one of the materials. When any conducting material comes in contact with the charged material, electrostatic discharge occurs, transferring electrons to the third material. Since electronic components used in control systems are designed to carry very low voltages, as little as a 30-volt charge created by static electricity can cause a total or degrading failure in ECM or other electronic components containing integrated circuits. Before servicing ECM, ground yourself and ground the work area to discharge stored electricity. |
| Movement Causing Charge | Relative Humidity 10-20% | Relative Humidity 65-90% |
|---|---|---|
| Walking Across Carpet | 35,000 | 1500 |
| Handling Clear Plastic Bag | 20,000 | 1200 |
| Sliding Across Velour Seat | 15,000 | 400 |
| Walking Across Tile/Vinyl | 12,000 | 50 |
| Handling Vinyl Envelope | 7000 | 600 |
STATIC CHARGE (VOLTS)
| CAUTION | DO NOT remove part from packaging until ready to install. Ground any static proof package PRIOR to opening. DO NOT touch electrical terminals of components unless properly grounded. DO NOT lay electrical components on car seat, carpeting or dashboard. Use electrostatic protection mat and ground strap whenever possible. (Scheme 1) |
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) Incorrect MEM-CAL installation procedure.
- 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.
- Inspect the MEM-CAL to determine if a cork spacer is glued to the top side of the MEM-CAL assembly. If so, remove it prior to installation.
- Align small notches with matching notches in the ECM MEM-CAL socket.
- 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.
- 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.
- 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.
- Remove ECM from vehicle as previously outlined. 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.
- 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.
- 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 with small notch and (1). (Scheme 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.
- If Code 51 is stored, or if "SERVICE ENGINE SOON" light stays on constantly with no codes, 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 & CALPAK in ECM (Except 2.5L). Scheme 2
Remove ECM from vehicle as previously outlined. Remove access cover. Note location of reference notch in CALPAK and ECM for reassembly reference. Engage narrow ends of CALPAK carrier with removal tool. Gently rock carrier from end-to-end while applying firm upward pressure.
Note. CALPAK carrier should ONLY be removed with special CALPAK removal tool. Use of any other method may damage CALPAK or CALPAK socket.
- Check that new CALPAK has same service number as the one being replaced. Place new CALPAK and carrier in ECM. Press on CALPAK carrier until CALPAK is firmly seated in ECM. Make sure that reference notch in ECM and CALPAK are properly aligned with smaller notch and (1). (Scheme 2)
- Install 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 CALPAK installation.
- If Code 52 is stored, or if "SERVICE ENGINE SOON" light stays on constantly with no codes, CALPAK is not fully seated in ECM, is installed backward, has bent pins or is defective. If pins are bent and crack when straightened, CALPAK must be replaced. If CALPAK is installed backward or is defective, it must be replaced.
Remove ECM from vehicle as previously outlined. Remove access cover. Using two fingers, push both retaining clips away from MEM-CAL unit and lift it out of socket by grasping both ends of MEM-CAL unit. (Scheme 3) DO NOT remove cover from MEM-CAL unit.
Replacing MEM-CAL in Electronic Control Module (2.5L Only). Scheme 3
Note. MEM-CAL unit can ONLY be removed in this manner. Use of any other method may damage MEM-CAL or MEM-CAL socket.
- Check that new MEM-CAL has same service number as the one being replaced. Place new MEM-CAL in ECM. Press on ends of MEM-CAL until retaining clips snap into ends of MEM-CAL unit. DO NOT press on middle of MEM-CAL unit, only the ends. Make sure that small notches in MEM-CAL socket and MEM-CAL are properly aligned. (Scheme 3)
- Install 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 MEM-CAL installation.
- If Code 51 is stored, or if "SERVICE ENGINE SOON" light stays on constantly with no codes, MEM-CAL is not fully seated in ECM, is installed backward, has bent pins or is defective. If pins are bent and crack when straightened, MEM-CAL must be replaced. If MEM-CAL is installed backward or is defective, it must be replaced.
OXYGEN (O2) SENSOR
Note. Oxygen sensor uses a permanently attached pigtail and connector. DO NOT remove pigtail or connector from sensor, as sensor operation could be impaired. Also, keep in-line connector and louvered end of sensor free of grease, dirt, or other contaminants. Avoid dropping or rough handling of sensor.
Disconnect negative battery cable at battery. Raise vehicle, if required. Disconnect electrical connector from oxygen sensor. Carefully remove O2 sensor from exhaust pipe.
Note. Oxygen 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.
- Whenever an O2 sensor is removed, its threads must be coated with anti-seize compound (3613695 ) before it is installed. New sensors will already have this compound applied to threads.
- 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.
Removal (2.5L Engine Only)
Remove air cleaner assembly. Discard gasket. Disconnect electrical connector from TPS. Remove 2 TPS attaching screws, lock washers, and retainers. Remove TPS.
- With throttle valve in normal closed position, install TPS on throttle shaft. Rotate TPS counterclockwise to align mounting holes. Install TPS screws, lock washer, and retainers. Tighten screws to 18 INCH lbs. (2.0 N.m). Connect electrical lead. Replace gasket and install air cleaner. Perform OUTPUT CHECK.
Note. Throttle position sensor is nonadjustable. Only output voltage can be monitored.
Output Check
Connect digital voltmeter between center "B" terminal and outside terminal "A" of TPS connector. Read TPS voltage with ignition on, engine off. If voltage is more than 1.25 volts, check minimum idle speed before replacing TPS.
Removal (Except 2.5L Engine)
Note. TPS on 2.8L and 7.4L engines has horizontal electrical connector. On all other engines, TPS has vertical electrical connector.
Remove air cleaner, adapter, and gaskets. Discard gaskets. Disconnect electrical connector from TPS. Remove 2 TPS attaching screws, lock washers, and retainers (if equipped). Remove TPS.
With throttle valve in normal closed position, install TPS on throttle body. Ensure TPS lever is aligned with TPS drive lever on throttle body. Install screws, lock washers, and retainers. Connect electrical lead. Replace gasket and install air cleaner. On 2.8L engine, perform OUTPUT CHECK.
Note. Throttle position sensor on all models except 2.8L engine is nonadjustable. Only output voltage can be monitored on these engines.
Output Check (2.8L Engine)
Connect digital voltmeter between center "B" terminal and outside terminal "A" of TPS connector. Read TPS voltage with ignition on, engine off. If voltage is not .42-.54 volts, rotate TPS until specification is obtained. If specification cannot be obtained, replace TPS.
Output Check (Except 2.8L Engine)
Connect digital voltmeter between center "B" terminal and outside terminal "A" of TPS connector. Read TPS voltage with ignition on, engine off. If voltage is more than 1.0 volt, check minimum idle speed before replacing TPS.
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.
Note. In the following diagnostic charts, illustrations and flow- charts are supplied courtesy of General Motors Corp.
