Jeep Repair: OBD II code scanner connection problems, obd ii code scanner, obd ii code

Question
QUESTION: I have a 1997 Jeep Wrangler with a four cylinder engine and manual transmission.  I have been trying to get my code reader to connect through the data link connector.  I replaced the fuse and it worked once or twice but since then it has been giving a "failure to connect" message.  The tech line for the scanner suggested that an aftermarket radio could cause problems and so I took the radio out.  They also said to check pins 4, 5 and 16.  Pins 4 and 5 have a good ground with less than 3 ohms, and pin 16 has more than 12.5 volts.  I am at a loss at to what to check next.

ANSWER: go to an auto parts store and see if they will hook up there scanner to see if it will work  if it does  its your scanner  if not  then get back to me.

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QUESTION: I thought about the scanner being the problem, however I am able to plug the scanner into my 2001 Dodge truck and 1998 Ford and it reads every time.

Answer
DATA LINK CONNECTOR CAV CIRCUIT FUNCTION
1 - -
2 - -
3 D1 20VT/BR CCD BUS(+) 2.5v
4 Z12 20BK/LB GROUND
5 Z12 20BK/TN GROUND
6 D20 20LG SCI RECEIVE
7 D21 20PK SCI TRANSMIT
8 - -
9 - -
10 - -
11 D2 20WT/BK CCD BUS(-)  2.5v
12 - -
13 - -
14 - -
15 - -
16 M1 20PK/WT FUSED B(+)   12V