Instruments and Controls Identification blink code diagnostics are activated. See Group 42 of the Heavy-Duty Trucks Service Manual for trouble- shooting procedures. IF REAR WHEEL SPIN OCCURS, PARTIALLY RELEASE THROTTLE PEDAL UNTIL WHEEL SPIN AMBER LIGHT EXTINGUISHES, THEN ENGAGE AXLE LOCK. IMPORTANT: ABS and ATC blink code diagnos- tics should only be performed when the vehicle is stopped. If the vehicle is equipped with ATC, turning "on" the ABS CHK switch will reduce engine speed to idle for three seconds and af- fect ATC function performance. If the vehicle is driven with the ABS CHK switch "on" (in the "up" position), the WHL SPIN light will illuminate continuously.
Under this condition, turning the ABS CHK switch "off" (in the "down" position), while the vehicle is still in motion, will only turn off the WHL SPIN light, but will not restore ATC function performance. To fully restore engine and ATC function capability, the vehicle must be brought to a complete stop. Then, move the ABS CHK switch to "off" (in the "down" posi- tion). 09/22/98 f600311a Fig. 2.21, Dash Label these vehicles, the ATC system automatically con- trols wheel spin during reduced-traction starts. An "ATC Function" switch (if equipped), allows the driver to select from two levels of drive axle traction- control assistance:
NORMAL—which reduces drive axle wheel spin on icy, wet, or sand covered roads. DEEP SNOW/MUD—which allows a higher threshold of drive axle wheel spin to help burn through a thin layer of ice, or to help throw off accumulated mud or snow. See the brake system operating instructions in Chap- ter 6 for more information. The Deep Snow/Mud mode is indicated by a flashing WHL SPIN light. To engage this mode, the ATC func- tion switch must be in the Normal position when the vehicle is initially powered up. Once the vehicle is started, the ATC function switch can be set to the Deep Snow/Mud position.
The ECU indicates this change by a constant flashing of the WHL SPIN lamp (or by illumination of the Deep Snow/Mud light on vehicles built before July, 1994). Bendix Antilock Braking System (ABS) With the Bendix Antilock Braking System (ABS), the tractor warning light (TRAC ABS) comes on after the key is turned on ( Fig. 2.19 ). The warning light goes out only if all of the tractor’s ABS components are working properly. If the ATC function switch is in the Deep Snow/Mud position when the vehicle is powered up, the ECU will not accept this function change and will remain in the Normal mode.
Indication of this condition will be the absence of the flashing WHL SPIN light (on ve- hicles built before July, 1994, the absence of an illu- minated Deep Snow/Mud light). To engage the Deep Snow/Mud mode in this situation, change the position of the ATC function switch to the Normal mode. After two seconds, move the switch to the Deep Snow/ Mud position. When this occurs, the indicator light will activate as previously described. If the tractor is attached to a trailer with a compatible ABS system, the trailer ABS warning lamp (TRLR ABS) will also come on momentarily after the key is turned on.
Vehicles equipped with a Bendix ABS system may also be equipped with an automatic traction control (ATC) system. The ATC system automatically con- trols wheel spin during reduced-traction starts. The wheel spin indicator light (WHL SPIN) comes on if one of the drive wheels spins during acceleration ( Fig. 2.19 ). The light goes out when the wheel stops spinning. The Bendix system will either reduce en- gine torque or apply gentle brake pressure to force the differential to drive the stationary or slowly spin- ning wheel. If slippery road conditions continue, en- gage the axle lock.
The "ABS Chk" switch (if equipped), activates blink code diagnostics, which are used to read ABS and ATC system fault codes on the WHL SPIN light. This switch is located in the lower dash panel cover, just below the ignition switch, on the left side of the steer- ing wheel. When turned on (in the "up" position), 2.15