Generic Electronic Module (GEM)
SECTION 419-10: Multifunction Electronic Modules
2001 F-Super Duty 250-550/Excursion/F-53 Motorhome Chassis Workshop Manual
DIAGNOSIS AND TESTING
Procedure revision date: 06/21/2000
Generic Electronic Module (GEM)
Special Tool(s)
73III Automotive Meter
105-R0057 or equivalent
Worldwide Diagnostic System (WDS)
418-F224
New Generation STAR (NGS) Tester
418-F052 or equivalent diagnostic tool
Principles of Operation
The following is list of GEM controlled functions:
Ignition Switch Positions
The position of the ignition switch is very important to correct GEM operation. The following is a brief description of five ignition switch positions.
When the ignition switch is in the RUN position, battery voltage should be present at the GEM RUN and RUN/ACC input terminals.
When the ignition switch is in the ACC position, battery voltage should be present at the GEM RUN/ACC input terminal only.
When the ignition switch is in the START position, battery voltage should be present at the GEM start/clutch depressed input.
The GEM module does not have an OFF or LOCK switch state input. The GEM will assume the OFF or LOCK position when there are no RUN, ACC, or START signals present.
Inspection and Verification
Electrical
Central junction box (CJB) fuse:
Connector(s)
Circuitry
Symptom Chart
Symptom Chart
Condition Possible Sources Action
Pinpoint Tests
PINPOINT TEST A: NO COMMUNICATION WITH THE GENERIC ELECTRONIC MODULE (GEM)
CONDITIONS DETAILS/RESULTS/ACTIONS
A1 CHECK CIRCUIT 1052 (TN/BK) FOR VOLTAGE
1.
2.
Central Junction Box C243
3.
3. Measure the voltage between central junction box C243, circuit 1052 (TN/BK) and ground.
GO to A2.
→ No
REPAIR the circuit. REPEAT the self-test.
A2 CHECK CIRCUIT 875 (BK/LB) FOR CONTINUITY TO GROUND
1.
GEM C239
2.
2. Measure the resistance between GEM C239 pin 26, circuit 875 (BK/LB), and ground.
REFER to Module Communications Network.
→ No
REPAIR the circuit. REPEAT the self-test.
Copyright ©2019 by Chilton, an imprint of Cengage Learning
SECTION 419-10: Multifunction Electronic Modules
2001 F-Super Duty 250-550/Excursion/F-53 Motorhome Chassis Workshop Manual
DIAGNOSIS AND TESTING
Procedure revision date: 06/21/2000
Generic Electronic Module (GEM)
Special Tool(s)
73III Automotive Meter
105-R0057 or equivalent
Worldwide Diagnostic System (WDS)
418-F224
New Generation STAR (NGS) Tester
418-F052 or equivalent diagnostic tool
Principles of Operation
The following is list of GEM controlled functions:
- 4-wheel drive functions
- front and rear wiper/washer
- warning chimes
- keyless entry
- interior and exterior lamps
- power windows
Ignition Switch Positions
The position of the ignition switch is very important to correct GEM operation. The following is a brief description of five ignition switch positions.
When the ignition switch is in the RUN position, battery voltage should be present at the GEM RUN and RUN/ACC input terminals.
When the ignition switch is in the ACC position, battery voltage should be present at the GEM RUN/ACC input terminal only.
When the ignition switch is in the START position, battery voltage should be present at the GEM start/clutch depressed input.
The GEM module does not have an OFF or LOCK switch state input. The GEM will assume the OFF or LOCK position when there are no RUN, ACC, or START signals present.
Inspection and Verification
- Verify the customer concern by operating the system.
- Visually inspect for obvious signs of electrical damage.
Electrical
Central junction box (CJB) fuse:
- 8 (5A)
- 15 (5A)
Connector(s)
Circuitry
- If the concern remains after the inspection, connect the diagnostic tool to the data link connector (DLC) located beneath the instrument panel and select the vehicle to be tested from the diagnostic tool menu. If the diagnostic tool does notcommunicate with the vehicle:
- check that the program card is correctly installed.
- check the connections to the vehicle.
- check the ignition switch position.
- If the diagnostic tool still does not communicate with the vehicle, refer to the diagnostic tool manual.
- Carry out the DATA LINK DIAGNOSTICS test. If the diagnostic tool responds with:
- CKT914, CKT915 or CKT70 = ALL ECUS NO RESP/NOT EQUIP, refer to Module Communications Network.
- NO RESPONSE/NOT EQUIP for GEM, go to pinpoint Test A.
- SYSTEM PASSED, retrieve and record the continuous diagnostic trouble codes (DTCs), erase the continuous DTCs and carry out self-test diagnostics for the GEM.
- If the DTCs retrieved are related to the concern, go to the Diagnostic Trouble Code (DTC) Index to continue diagnostics.
- If no DTCs related to the concern are retrieved, refer to the appropriate section of the Workshop Manual to continue diagnostics.
Symptom Chart
Symptom Chart
Condition Possible Sources Action
- No communication with the generic electronic module (GEM).
- Central junction box (CJB) fuse 15 (5A).
- Circuitry.
- GEM
- GO to Pinpoint Test A.
Pinpoint Tests
PINPOINT TEST A: NO COMMUNICATION WITH THE GENERIC ELECTRONIC MODULE (GEM)
CONDITIONS DETAILS/RESULTS/ACTIONS
A1 CHECK CIRCUIT 1052 (TN/BK) FOR VOLTAGE
1.
2.
Central Junction Box C243
3.
3. Measure the voltage between central junction box C243, circuit 1052 (TN/BK) and ground.
- Is the voltage greater than 10 volts?
GO to A2.
→ No
REPAIR the circuit. REPEAT the self-test.
A2 CHECK CIRCUIT 875 (BK/LB) FOR CONTINUITY TO GROUND
1.
GEM C239
2.
2. Measure the resistance between GEM C239 pin 26, circuit 875 (BK/LB), and ground.
- Is the resistance less than 5 ohms?
REFER to Module Communications Network.
→ No
REPAIR the circuit. REPEAT the self-test.
Copyright ©2019 by Chilton, an imprint of Cengage Learning