On-board Radio Diagnostic

Having become the proud owner of a 2000-2001 L series shop manual (and
because Engineers just like to find out how things work) I was looking for
the source of some radio interference. I hit a low hanging tree branch a
while back and the radio has gotten more susceptible to interference when
the engine is running (not spark noise but HF computer type noise).

Suspected that the antenna was damaged and was going to borrow one to swap
out but found a more exact method, the onboard radio diagnostic. My car has
the AM/FM/CD/Tape uplevel model. (bought it used and that's the way it
came).

Enter the diagnostic from the radio on (either am or fm) and simultaneously
press RCL + 1 + 6 while pressing off button.

Radio will beep to show diagnostic mode.

Display will show 'DTC'
Diagnostic trouble code memory.
Press RCL to show E-01 and RCL again to show the number of errors
experienced.
Press am/fm to back up to E-xx and use seek to select another code.
continue as before to find all codes.
When done, hit am/fm to return to DTC top menu.

Error codes:
E-01 Tape eject error
E-02 Tape play error
E-03 Tape insertion error
E-04 CD eject error
E-05 CD play error
E-06 CD insertion error
E-07 CD changer error
E-08 CD changer magazine loading error
E-09 CD changer play error

==============

Back at the DTC display, hit the SEEK rocker to sequence to the next
diagnostic:
DTC => TT => LCD => KEY => EQ:__ => ANT => CDCH => CC

At each diagnostic, hit RCL to enter and am/fm to back out.

TT: test tone. hit RCL to begin test. A 100Hz tone is sent to the left front
speaker for 2 seconds followed by a 3kHz tone. Press the TUNE button to
cycle from the LF to RF to LR antd to RR speakers
Press am/fm to escape back to menu.

LCD: Display segment test. Press RCL to light all segments.
Press am/fm to escape to menu.

Key: Key test. Press RCL and press keys. A beep is heard for each key press.
Press am/fm to escape to menu.

EQ: Displays which audio system the radio is connected to.
RCL am/fm

ANT: Press RCL to display the received signal strength of the last station
tuned. Tuning controls are locked out for this test so set a station of
interest before entering diagnostic mode.
Press am/fm to escape to menu.

CCDH: CD changer communication. Hit RCL to test communication. If changer
not installed, ERR displays.
Press am/fm to escape to menu.

CC: Clear Error codes. Clears error codes displayed under DTC. Press RCL and
display shows OK?. press RCL again for 2 seconds until confirmation tone is
heard to clear codes.
Press am/fm to escape to menu.

To exit diagnostic mode, hit power off.

==============

Word of caution, watch out for inadvertantly setting the Theft Deterrent
security mode. Ignition on, radio off, press and hold buttons 5 and 6 until
the radio shows _ _ _ _. This procedure is given in the owner's manual.
Radios are delivered in the unsecured state. If the secured mode is chosen,
you have to enter a 4 digit code to lock it. Owner will need to make the
code available for service personnel or unsecure it for service.
Sounds like a pain.