E. General Information/Precautions

The HHT can be used for diagnosis of many vehicle Systems in current production models. In models equipped with a 38-pole data link connector (X11/4), the HHT is connected to the vehicle via a multiplexer cable. With the multiplexer cable connected to X11/4, the engine hood can not be closed. Closing the hood will damage the hood, multiplexer cable, data link connector, module box, etc.. If a road test is required while using the HHT, use the "driving" cable designed for this purpose.

On model 124 vehicles with the 16-pole data link connector (X11/4), the 4-pole "124" adapter cable must be used in place of the multiplexer cable. Model 129 vehicles with the 16-pole data link connector cannot be diagnosed with the HHT.

Vehicle systems diagnosable with the HHT can be tested individually, or all systems at once by means of a "Quick Test" (vehicles with 38-pole X11/4 only).

HHT Internal Battery Information

The internal battery of the HHT (located in the handle) is used to maintain the internal clock and calendar. The internal battery does not provide power to the HHT. Operating power is supplied directly from the vehicle while the HHT is connected.

Refer to HHT Operating Instructions for correct battery type to be used. Never use normal alkaline batteries.

Note:
^ The HHT will continue to function even if the battery is not installed.

^ If the internal battery is installed, but is not at full operating voltage, an error message for the battery test mode may appear. Low internal battery voltage can occur if the HHT is not used for several weeks. To recharge the internal battery, connect the HHT to a vehicle with the multiplexer cable and the ignition OFF. Leave the HHT connected for at least half an hour.

To open the battery compartment and install the battery, follow the numbered sequence below.

PRECAUTIONS

! IMPORTANT - FIRST TIME USERS!
DO NOT use the HHT without proper instruction by your Technical Training Centers or Regional Personnel.

! WARNING!
When performing a road test which requires the use of the HHT, ALWAYS use the "driving" cable and make sure the engine hood is completely closed. Diagnosis using the HHT during a road test should not be performed by the driver but by an accompanying technician.

! CAUTION!
Observe the following conditions to prevent extensive damage to the HHT:

^ DO NOT connect the HHT with the vehicle ignition ON!

^ ALWAYS connect the multiplexer cable to the HHT first and then to the data link connector!

^ NEVER connect the HHT to household/shop current (110/220 V).

^ The permissible operating temperature range of the HHT is -4°F to 104°F. The permissible storage temperature range is -220°F to 176°F.

^ Always keep the HHT away from strong electromagnetic fields (such as that generated by electrical welding equipment).

^ DO NOT expose the HHT to water or other agents such as brake fluid, thinners, acid etc.

^ Ensure that the contacts of the HHT module are kept clean and damage-free.