Test B14 - Brake On/Off Switch (Boo)

NOTE: Perform this test when Service Code 74 or 75 is displayed during QUICK TESTS or when directed here by other test procedures.

Fig 1: Vehicle Speed Sensor Circuit

To prevent replacement of good components, be aware that the following non-EEC related areas may be at fault: brake light bulb, brake light switch, or brake light fuse.

Code 74 Displayed - If brake was NOT depressed during KOER SELF-TEST, repeat test and depress brake pedal ONLY once during test. Depress and release brake pedal AFTER dynamic response code 1 (10 on STAR tester) but before brief WOT. If pedal was depressed, go to next step.
Checking Power Circuit - Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect connector for damaged pins, corrosion, and loose wires. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Measure voltage between Test Pins No. 2 and 40 while applying and releasing brake. If voltage cycles, replace ECA and repeat QUICK TEST . If voltage does not cycle, go to next step.
Checking For Shorts To Ground - Turn key off. Leave breakout box installed and ECA disconnected. Set DVOM on 200K-ohm scale. Disconnect BOO circuit at 12-pin connector (14290 Harness). Measure resistance between Test Pin No. 2 and 40. If resistance is greater than 10K ohms, go to next step. If resistance is less than 10K ohms remove breakout box repair short, and repeat KEY ON ENGINE RUNNING (KOER) SELF-TEST .
Code 75 Displayed - Turn key off and wait 10 seconds. Disconnect ECA 60-pin connector. Inspect for and repair any damaged wiring. Install breakout box, leaving ECA disconnected. Set DVOM on 200-ohm scale. Disconnect BOO from Transmission Hydraulic Switch 12-pin connector (14290 Harness). Measure resistance between Test Pin No. 2 and BOO circuit at the 12-pin connector (14290 Harness). If resistance is greater than 5 ohms, remove breakout box. Reconnect ECA, repair open circuit, and rerun SELF-TEST.
Code 75: Cycle BOO Circuit - Turn key off. With breakout box installed and ECA disconnected, set DVOM on 20-volt scale. Measure voltage between Test Pins No. 2 and 40 at the breakout box while depressing and releasing the brake pedal. If voltage cycles, remove breakout box. Replace ECA, and rerun QUICK TEST . If voltage does not cycle go to next step.
Checking BOO Circuit For Short To Power - Turn key off. Install breakout box, leaving ECA disconnected. Set DVOM on 20-volt scale. Disconnect BOO circuit at 12-pin connector. Measure voltage between Test Pin No. 2 at the breakout box and engine block ground. If voltage is greater than 10.5 volts, BOO circuit is okay. Check and repair brake light circuit as necessary. If voltage is less than 10.5 volts, remove breakout box. Reconnect ECA, repair circuit short and rerun QUICK TEST .