Ametek 387 - 5.5.3 Sev eral (But Not All) Gauge Pointers Sweep 5-27; 5.5.4 SMC Pointer and All J1708 Data Bus Gauge Pointers Sweep 5-27

verify the Interface Module is correctly configured for that gauge. If not,
reconfigure as appropriate.
d. If the Interface Module is correctly programmed for that pressure gauge
and data is still not present on the private data bus, replace the Interface
Module.
5.5.3 Several (But Not All) Gauge Pointers Sweep
Probable Cause - The private data bus + or – wires are open between the gauges.
Procedure:
1. Locate the first gauge in the daisy chain that is not working and verify its connec-
tors are fully engaged.
2. Unplug both connectors and inspect their pins and the gauge receptacle for bent
or missing pins. Replace the gauge or the 5-wire cable assembly if damaged.
3. If no damage is evident, replace the 5-wire cable assembly that connects the first
defective gauge to the last gauge on the daisy chain that works.
4. If the problem still is not corrected, then the last working gauge on the daisy
chain could have an internally damaged connector. Replace that gauge.
5.5.4 SMC Pointer and All J1708 Data Bus Gauge Pointers Sweep
Symptoms - The SMC pointer and the pointers of all public bus gauges sweep; the
SMC displays NO DATA.
Note:
It can take as long as 2
1
2
minutes to display NO DATA.
Probable Cause - The J1708 data bus from the Engine ECU to the Interface Module
and the SMC is open (broken wire or connector pin); defective Interface Module; de-
fective SMC; defective Engine ECU or other device connected to the J1708 data bus.
Procedure: (see Figure 5-14 on page 5-28.)
1. Perform the checks in Figure 5-14 on page 5-28. If the reading is less than about
10 ohms, another device using the J1708 data bus (SMC, Interface Module, ABS,
Transmission or HVAC ECU, satellite communications devices, etc.) could be de-
fective and interfering with bus communications. Continue with the next step.
2. To find which device may be interfering with data bus communications, switch
the ignition off and disconnect the devices from the J1708 data bus as follows:
a. Locate the splice block behind the glove box and unplug all devices at
the splice block except the Engine ECU.
b. Disconnect the Interface Module by unplugging 10-pin connector J3 at
the module.
c. Disconnect the SMC by unplugging the six-pin connector from the rear
of the SMC.
Model 387 Instrument System Service Manual
072-40245 B 5-27 Troubleshooting Procedures