Section 17-04: Lamps, Daytime Running
1994 Mustang Workshop Manual
DIAGNOSIS AND TESTING

Pinpoint Tests

  

PINPOINT TEST A: HIGH BEAMS INDICATOR ON, HIGH BEAMS ON FULL INTENSITY OR HIGH BEAMS INOPERATIVE

 

A1 CHECK PARKING BRAKE CIRCUIT

Yes
SERVICE parking brake signal switch and bracket as necessary. RESTORE vehicle. RETEST System.

No
GO to A2 .

 

A2 CHECK DRL MODULE SUPPLY

Yes
GO to A4 .

No
GO to A3 .

 

A3 CHECK IGNITION SUPPLY CIRCUIT TO DRL MODULE

  • Using test lamp, check for voltage at output side of fuse 1 (15A).
  • Did test lamp illuminate?
Yes
SERVICE Circuit 298 (P/O) for open circuit. RESTORE vehicle. RETEST system.

No
SERVICE fuse 1 (15A) as necessary. RESTORE vehicle. RETEST system.

 

A4 CHECK BATTERY FEED TO DRL MODULE

  • Using test lamp, check for voltage to Pin 4, Circuit 477 (LB/BK) at DRL control connector.
  • Did test lamp illuminate?
Yes
GO to A5 .

No
SERVICE Circuit 477 (LB/BK) for open circuit. RESTORE vehicle. RETEST system.

 

A5 CHECK FOR LOW BEAM INPUT

  • Using test lamp, check for voltage at Pin 7, Circuit 13 (R/BK) at DRL control connector.
  • Did test lamp illuminate?
Yes
SERVICE Circuit 13 (R/BK) for short to voltage. RESTORE vehicle. RETEST system.

No
REPLACE daytime running lights control . RESTORE vehicle. RETEST system.

  

PINPOINT TEST B: HIGH BEAMS ON AT REDUCED INTENSITY WITH IGNITION OFF

 

B1 CHECK IGNITION SWITCH INPUT

  • With ignition switch off, use a test lamp and check for voltage at Pin 2, Circuit 298 (P/O) at daytime running lights control.
  • Did test lamp illuminate?
Yes
GO to B2 .

No
REPLACE daytime running lights control . RESTORE vehicle. RETEST system.

 

B2 CHECK CIRCUIT 298 (P/O)

  • Remove Fuse 1 (15A).
  • Using a test lamp, check Circuit 298 (P/O) for voltage at Pin 2 at daytime running lights control.
  • Did test lamp illuminate?
Yes
SERVICE Circuit 298 (P/O) for short to voltage. RESTORE vehicle. RETEST system.

No
REFER to Section 11-05.

  

PINPOINT TEST C: HIGH BEAMS ON AT REDUCED INTENSITY WITH PARKING BRAKE APPLIED

 

C1 CHECK PARKING BRAKE SIGNAL SWITCH AND BRACKET

  • Turn ignition switch to RUN, turn headlamps off.
  • Disconnect parking brake signal switch and bracket.
  • Using a jumper wire, connect Circuit 22 (LB/BK) to a known good ground.
  • Did high beams turn off?
Yes
REPLACE parking brake signal switch and bracket . RETEST system.

No
GO to C2 .

 

C2 CHECK CIRCUIT 22 (LB/BK)

  • With jumper wire still connected, disconnect daytime running lights control .
  • Using an ohmmeter connected to a known good ground, measure resistance of Circuit 22 (LB/BK).
  • Is resistance 5 ohms or less?
Yes
REPLACE daytime running lights control . RESTORE vehicle. RETEST system.

No
SERVICE Circuit 22 (LB/BK) for open circuit. RESTORE vehicle. RETEST system.

  

PINPOINT TEST D: HIGH BEAMS AT REDUCED INTENSITY WITH HEADLAMP SWITCH ON

 

D1 CHECK DRL MODULE

  • Turn ignition switch to RUN. Disconnect DRL control connector.
  • Did headlamps turn off?
Yes
REFER to Section 17-01. SERVICE as necessary.

No
REPLACE daytime running lights control . RESTORE vehicle. RETEST system.

  

PINPOINT TEST E: NO HIGH BEAM INDICATOR WITH HEADLAMPS IN HIGH BEAM POSITION

 

E1 CHECK HIGH BEAM INDICATOR LAMP

  • Remove high beam indicator lamp at instrument cluster . Carefully inspect the bulb.
  • Is bulb burned out or damaged?
Yes
REPLACE indicator lamp bulb. RESTORE vehicle. RETEST system.

No
GO to E2 .

 

E2 CHECK CIRCUIT 932 (GY/W) FOR VOLTAGE

  • Reinstall high beam indicator lamp.
  • Turn ignition switch to RUN, actuate turn indicator levers to high beam.
  • Using a test lamp, check for voltage at Pin 1, Circuit 932 (GY/W).
  • Did test lamp illuminate?
Yes
SERVICE Circuit 932 (GY/W) for open circuit. RESTORE vehicle. RETEST system.

No
GO to E3 .

 

E3 CHECK DRL CONTROL

  • Using a jumper wire, connect one end to Pin 8, Circuit 12 (LG/BK), connect other end to Pin 1, Circuit 932 (GY/W).
  • Did high beam indicator illuminate?
Yes
REPLACE daytime running lights control . RESTORE vehicle. RETEST system.

No
GO to Section 13-01. SERVICE as necessary.