What this code means
B1664 means the rear interior LF antenna circuit may have an open connection.
B1664 concerns an open connection in the rear interior LF antenna circuit. The procedure considers the antenna's connecting paths and the body control module circuit. Its purpose is to use those checks to identify the remaining fault area.
An open connection is an interruption in the electrical path being tested. The location of that interruption is determined through the connector and wire checks, rather than by treating the antenna name in the code as a complete diagnosis.
What the vehicle may do
- The rear antenna circuit may have an open connection.
Possible fault areas
- The rear antenna circuit wiring may have a problem.
- The body control module may have a problem.
- The rear antenna may have a problem.
The displayed sequence starts with the self-check and the individual EXT_R wire inspections. The procedure also permits the body-control-module circuit check to be performed before the other inspections because that check includes them. If that overall check is abnormal, the individual inspections are then used as directed.
This gives the module-circuit result and the separate wire results different roles. Follow the stated branch for whichever permitted starting point is used, while retaining the connector preparation and the individual normal criteria.
Diagnostic path
Understand the stored condition
B1664 means Rear Interior LF Antenna Circuit Open. The rear antenna circuit may have an open connection.
Start with the self-check
Before you troubleshoot, review the How to Troubleshoot guidance. If you are troubleshooting multiple DTCs, follow B-CAN System Diagnosis Test Mode A first. For B1664, run the HDS Self Check. Select One-Push Start > Keyless Access Control Unit > Self Check.
Prepare the circuit connections
Disconnect the rear interior LF antenna connector (2P). Then disconnect body control module connector C (66P).
Check the EXT_R+ wire
Before you check resistance on EXT_R+, set IG Mode OFF.
- First probe: rear interior LF antenna connector (2P) female terminal 2.
- Other probe: body control module connector C (66P) female terminal 29.
The reading should be less than 1 ohm. If it is below 1 ohm, this wire checks normal.
EXT_R+ pairs antenna connector terminal 2 with body control module connector C (66P) terminal 29. EXT_R- pairs antenna terminal 1 with module terminal 28. The less-than-1-ohm criterion belongs to those individual paths under the stated disconnected-connector and IG conditions.
The module-circuit check uses a different kind of result: voltage present. That qualitative result is applied as written. It should remain separate from the numerical wire-resistance criterion, so the overall circuit check and the individual path checks keep their respective meanings.
Check the EXT_R- wire
Keep IG Mode OFF while you check resistance on EXT_R-.
- First probe: rear interior LF antenna connector (2P) female terminal 1.
- Other probe: body control module connector C (66P) female terminal 28.
The reading should be less than 1 ohm. If it is below 1 ohm, this wire checks normal. If either open-wire check is abnormal, there is a problem in the circuit.
Check the body control module circuit
The external circuit must be normal for this body control module check. You can also run this check before the other inspections because it includes all the following inspection items. But if it fails, you must check each inspection item individually to find which one failed. The listed module test specifies the disconnected rear interior LF antenna connector (2P), IG Mode ON, and a measurement between female terminals 2 and 1. The normal result is voltage present.
The linked footnote mentions vehicle mode ON or OFF (LOCK) and permanent power supply, but the wording is unclear. It does not say you can test in OFF or that vehicle mode does not matter. Before you take the measurement, clarify this vehicle-mode requirement. For the listed measurement, place one probe on female terminal 2 and the other probe on female terminal 1. If this internal circuit check is abnormal, there is a problem with the body control module.
Identify the remaining fault area
If all the other inspection items check normal, the remaining rear antenna is the cause. Under that condition, there is a problem with the rear antenna.
Takeaway
For B1664, you start with the self-check, check both circuit wires, then check the body control module and finally the rear antenna. The readings tell you which fault area applies.
Final check
The checks can identify a circuit problem, a body control module problem, or the rear antenna as the remaining cause.
Keep the self-check, the EXT_R path readings and the body-control-module circuit result identifiable as separate findings. The procedure permits the overall module-circuit check before the individual inspections. Whichever permitted route is used, follow the stated result branch and retain the preparation and criteria for each individual measurement.
