Impco HHI, Service Manual

Page: 118 / 485

118
DLC COMMUNICATION ERROR
The ECM 5 volt reference circuit powers the Spectrum diagnostic link cable. In the event that the 5 volt
reference signal is open or shorted to ground, you will not be able to connect to the system. If you are
unable to connect, follow the quick checks listed below:
Be sure you are using the correct password and latest software for the system you are connecting to.
Check the ECM system power and ground circuits. Refer to DTC 562 for the power schematic. Also
check for +12 volts switched power at ECM pin 45 with the ignition key ON.
Check for power at the DLC connector for + 5 volts between pin 1 and pin 2 with the ignition key in the
ON position.
You may still be able to retrieve a code using the blink code function if none of the above recommenda-
tions prove useful. In the event of a 5 volt reference signal malfunction, DTC 642 or DTC 643 should
set. If you find one of these codes using the blink code function, follow the DTC diagnostic chart rec-
ommendations for that specific DTC.
BLINK CODE FUNCTION
Although the DST is considered a required tool to access the DTC codes, codes may be retrieved with-
out a laptop computer using the blink code function. To enable this function follow the steps below:

Jump pins A and D at the DLC connector.

Turn the ignition key to the on position

The system will now enter the self diagnostic blink code mode. Be ready with pen and paper to
write down any codes that may be stored.

The ECM will flash the MIL indicator with a pause between represented numbers that represent
DTC codes. The sequence starts with code 1654. Code 1654 confirms the system has entered the
blink code mode. The ECM will flash code 1654 (3) times before displaying the actual DTC code
that may be set.
Example:
One short blink (pause) six short blinks (pause) five short blinks (pause) four short blinks.

If no DTC codes are found, the ECM will continue to flash 1654 only. This means no stored DTC
codes were found.

If one of the numbers in the DTC code is zero (0), no flash will occur to represent the zero value—it
will be represented as a short pause.