Mike's Workshop Manuals: Service manuals for every vehicle
Home >> Ford >> 2002 >> Excursion 7.3 F, RWD >> Repair and Diagnosis >> External Pages >> Different car >> Section 3 (Anti-Theft System - Passive) >> System Tests >> Test E: Anti-Theft Module Transceiver Defective Or Not Connected (DTC B1681)

Test E: Anti-Theft Module Transceiver Defective Or Not Connected (DTC B1681)

WARNING: This page is about a different car, the 2002 Ford Focus, 2001 Ford Focus, and 2000 Ford Focus. However, it is still accessible from the selected car via links, so may be relevant.
NOTE: If Powertrain Control Module (PCM) is replaced, PCM must be reprogrammed and all ignition keys MUST be programmed into PCM.
  1. Connect New Generation Star (NGS) tester to Data Link Connector (DLC). Using NGS tester, clear continuous DTCs. Turn ignition switch to OFF position, then to RUN position. Perform PCM self-test and retrieve continuous PCM DTCs. If DTC B1681 is retrieved, go to next step. If DTC B1681 is not retrieved, inspect circuits for loose or corroded connections. Clean and tighten as necessary. Inspect circuits for pinched or broken wires, and repair as necessary. If no problems are found, system is okay at this time.
  2. Turn ignition off. Disconnect Passive Anti-Theft System (PATS) transceiver module harness connector C390. Turn ignition switch to RUN position. Measure voltage at terminal No. 1 (Green/Red wire on 2000-01 or Green/Black wire on 2002) at PATS transceiver module harness connector C390. See Fig 1. If battery voltage exists, go to next step. If battery voltage does not exist, repair open in Green/Black wire. See WIRING DIAGRAMS . Clear DTCs and repeat PCM self-test.
  3. Turn ignition off. Measure resistance between ground and terminal No. 2 (Black/Yellow wire) at PATS transceiver module harness connector C390. If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, repair open in Black/Yellow wire. Clear DTCs and repeat PCM self-test.
  4. Connect PATS transceiver module harness connector C390. Turn ignition switch to RUN position. Using a voltmeter, backprobe at terminal No. 4 (White/Green wire) at PATS transceiver module harness connector C390. If voltage is 8 volts or less, go to next step. If voltage is greater than 8 volts, go to step  7.
  5. Turn ignition off. Disconnect PCM harness connector C415 and PATS transceiver module harness connector C390. Measure resistance between ground and terminal No. 4 (White/Green wire) at PATS transceiver module harness connector C390. If resistance is greater than 10 k/ohms, go to next step. If resistance is 10 k/ohms or less, repair short to ground in White/Green wire. See WIRING DIAGRAMS . Clear DTCs and repeat PCM self-test. If system fails again, replace PCM.
  6. Measure resistance of White/Green wire between terminal No. 4 at PATS transceiver module harness connector C390 and terminal No. 53 at PCM harness connector C415. See Fig 1 and Fig 2 . If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, repair open in White/Green wire. See WIRING DIAGRAMS . Clear DTCs and repeat PCM self-test.
  7. Connect PCM harness connector C415 and PATS transceiver module harness connector C390. Turn ignition switch to RUN position. Using a voltmeter, backprobe terminal No. 3 (Gray/Orange wire) at PATS transceiver module harness connector C390. If voltage is 8 volts or less, go to next step. If voltage is greater than 8 volts, replace PATS transceiver. See PASSIVE ANTI-THEFT SYSTEM TRANSCEIVER MODULE  under REMOVAL & INSTALLATION.
  8. Turn ignition off. Disconnect PCM harness connector C415. Measure resistance between ground and terminal No. 19 (Gray/Orange wire) at PCM harness connector C415. See Fig 1 and Fig 2 . If resistance is 10 k/ohms or less, go to next step. If resistance is greater than 10 k/ohms, go to step  10.
  9. Disconnect PATS transceiver module harness connector C390. Measure resistance between ground and terminal No. 3 (Gray/Orange wire) at PATS transceiver module harness connector C390. If resistance 10 k/ohms or less, repair short to ground in Gray/Orange wire. See WIRING DIAGRAMS . If resistance is greater than 10 k/ohms, replace PATS transceiver module. Clear DTCs and repeat PCM self-test.
  10. Ensure ignition switch is in OFF position. Disconnect PATS transceiver module harness connector C390. Measure resistance of Gray/Orange wire between terminal No. 19 at PCM harness connector C415 and terminal No. 3 at PATS transceiver module harness connector C390. See Fig 1 and Fig 2 . If resistance is 5 ohms or less, go to next step. If resistance is greater than 5 ohms, repair open in Gray/Orange wire. See WIRING DIAGRAMS . Clear DTCs and repeat PCM self-test.
  11. Connect PCM harness connector C415 and PATS harness connector C390. Using NGS tester, trigger PCM active command TRANSMIT SIGNAL to ON. Using a voltmeter, backprobe at terminal No. 3 (Gray/Orange wire) at PATS transceiver module harness connector C390. If voltage is 5 volts or less, replace PATS transceiver module. Clear DTCs and repeat PCM self-test. If voltage is greater than 5 volts, go to next step.
  12. Turn ignition off. Disconnect PCM harness connector C415 and PATS transceiver module harness connector C390. Turn ignition switch to RUN position. Measure voltage between ground and terminal No. 3 (Gray/Orange wire) at PATS transceiver module harness connector C390. If voltage is present, repair short to power in Gray/Orange wire. See WIRING DIAGRAMS . Clear DTCs and repeat PCM self-test. If voltage is not present, replace PCM. Reprogram encoded ignition keys. See ERASE ALL KEYS & PROGRAM 2 KEYS  under PROGRAMMING. Clear DTCs and repeat PCM self-test.
Fig 1: Identifying PATS Transceiver Module Harness Connector C390 Terminals
G98G12290Courtesy of FORD MOTOR CO.
Fig 2: Identifying PCM Harness Connector C415 Terminals
G96F31315Courtesy of FORD MOTOR CO.
scientia non olet · About Mike's Workshop Manuals