Coolant Temperature Gauge Needle Goes Past The Hot Mark

Check for fuel and emissions related DTCs.
If you find any, repair the problem, and clear the DTC before continuing.
Jump the SCS line with the HDS.
Turn the ignition switch OFF.
Disconnect PCM connector B (56P).
Turn the ignition switch ON (II), and watch the coolant temperature gauge.
Does the temperature gauge needle stay on the cold mark? (you may have to watch it for about 30 seconds.)
1. YES - Substitute a known-good PCM and recheck, (see PCM UPDATING AND SUBSTITUTION FOR TESTING ). If the symptom/indication goes away, replace the original PCM.
2. NO - Go to step 6.
Turn the ignition switch OFF, and disconnect gauge assembly connector B (18P or 22P*).
*: '04-06 models
Check for continuity between gauge assembly connector terminal B3 (or B5*) and body ground.
*: '04-'06 models

Fig 1: Checking For Continuity Between Gauge Assembly Connector Terminal B3 And Body Ground ('03 Model)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Fig 2: Checking For Continuity Between Gauge Assembly Connector Terminal B5 And Body Ground ('04-06 Models)
Courtesy of AMERICAN HONDA MOTOR CO., INC.

Is there continuity?
1. YES - Repair short to ground PCM connector B6 and gauge connector terminal B3 (or B5*).
2. NO - Replace the fuel and temperature gauge assembly or the printed circuit board (PCB) ('03 model) or replace the gauge assembly ('04-06 models).
  *: '04-06 models