April 5, 2026: LEMON Manuals is launched! Read the announcement.

Pinpoint Test A: No Communication With The Generic Electronic Module (Gem)

CAUTION: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.

A1 CHECK THE GENERIC ELECTRONIC MODULE (GEM) POWER SUPPLY

Key in OFF position.
Disconnect: Generic Electronic Module (GEM) C201a.
Disconnect: GEM C201b.
Key in ON position.

Using the following table. measure the voltage between the GEM, harness side and ground.

GEM, HARNESS SIDE AND GROUND VOLTAGE

Connector	Pin	Circuit
C201a	4	400 (LB/BK)
C201a	1	1006 (DG/WH)
C201b	2	1001 (WH/YE)
C201b	3	193 (YE/LG)

Are the voltages greater than 10 volts?

Yes: GO to A2.
No: REPAIR the circuit(s) in question. TEST the system for normal operation.

A2 CHECK THE GEM GROUND CIRCUIT 397 (BK/WH) FOR OPEN
- Key in OFF position.
- Measure the resistance between the GEM C201b pin 4, circuit 397 (BK/WH), harness side and ground.
  
  Fig 1: Checking GEM Ground Circuit 397 (BK/WH) For Open
  Courtesy of FORD MOTOR CO.
- Is the resistance less than 5 ohms?
1. Yes: GO to A3.
2. No: REPAIR the cirucit(s) in question. TEST the system for normal operation.
A3 CHECK CIRCUIT 397 (BK/WH) FOR SHORT TO POWER
- Measure the voltage between the GEM C201b pin 4, circuit 397 (BK/WH), harness side and ground.
  
  Fig 2: Checking Circuit 397 (BK/WH) For Short To Power
  Courtesy of FORD MOTOR CO.
- Is any voltage present?
1. Yes: REPAIR the circuit. TEST the system for normal operation.
2. No: REFER to MODULE COMMUNICATIONS NETWORK .