Pinpoint Test X: The Reversing Lamps Are On Continuously
Reversing Lamps
Pinpoint Tests
Pinpoint Test X: The Reversing Lamps Are On Continuously
Refer to Wiring Diagram Set 93, Reversing Lamps for schematic and connector information. Diagrams By Number
Normal Operation
The reversing lamps relay coil ground is controlled by the PCM (automatic transmission, gasoline engine), the Transmission Control Module (TCM) (automatic transmission, diesel engine), or the reversing lamp switch (manual transmission).
For vehicles with an automatic transmission, when the transmission is in REVERSE (R), the PCM or TCM provide ground for the reversing lamps relay to energize.
For vehicles with a manual transmission, when the transmission is in REVERSE (R), the reversing lamp switch completes the ground path to energize the reversing lamps relay.
When the reversing lamps relay is energized, voltage is routed to the reversing lamps, the auto-dimming interior rear view mirror (if equipped), and through the Battery Junction Box (BJB) fuse 63 (15A) to the trailer reversing lamps.
- DTC P1910 (Reverse Lamp Control Circuit/Open) - an on-demand DTC that sets when the PCM (gasoline engine) or TCM (diesel engine) detects a short to ground from the reversing lamp relay coil ground control circuit.
This pinpoint test is intended to diagnose the following:
- Wiring, terminals or connectors
- Reversing lamps relay
- Reversing lamp switch (manual transmission)
- Interior rear view mirror
- TCM (automatic transmission, diesel engine)
- PCM (automatic transmission, gasoline engine)
PINPOINT TEST X: THE REVERSING LAMPS ARE ON CONTINUOUSLY
NOTICE: It is important to install relays in their correct position in the Battery Junction Box (BJB). Installing a relay incorrectly can cause wiring shorts or damage to modules. While carrying out diagnostics on BJB relays, have only one BJB relay removed at a time. Failure to follow these instructions can result in damage to the vehicle circuitry or to controlling modules.
NOTICE: Use the correct probe adapter(s) when making measurements. Failure to use the correct probe adapter(s) may damage the connector.
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X1 CHECK THE REVERSING LAMPS RELAY OUTPUT
- Ignition OFF.
- Disconnect: Reversing Lamps Relay.
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
If equipped with an auto-dimming interior rear view mirror, GO to X2.
If not equipped with an auto-dimming interior rear view mirror, GO to X3.
No
GO to X4.
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X2 CHECK THE INTERIOR REAR VIEW MIRROR
- Ignition OFF.
- Disconnect: Interior Rear View Mirror C911, C9012 or C9112.
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
GO to X3.
No
INSTALL a new interior rear view mirror. REFER to Mirrors. TEST the system for normal operation.
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X3 CHECK THE REVERSING LAMP RELAY OUTPUT CIRCUIT FOR A SHORT TO VOLTAGE
- Ignition OFF.
- Disconnect: BJB Fuse 63 (15A).
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
REPAIR circuit CLS10 (GN/BN) for a short to voltage. TEST the system for normal operation.
No
REPAIR circuit CAT03 (GY/BN) for a short to voltage. TEST the system for normal operation.
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X4 CHECK THE REVERSING LAMPS RELAY
- Ignition OFF.
- Substitute a known good relay.
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
REMOVE the known good relay. GO to X5.
No
REMOVE the known good relay. INSTALL a new reversing lamps relay. TEST the system for normal operation.
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X5 CHECK REVERSING LAMP RELAY COIL GROUND CONTROLLED CIRCUIT FOR A SHORT TO GROUND
- Connect: Reversing Lamps Relay.
- Disconnect: PCM C175b (Gasoline Engine, Automatic Transmission).
- Disconnect: TCM C1750 (Diesel Engine, Automatic Transmission).
- Disconnect: Reversing Lamp Switch C169 (Manual Transmission).
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
For vehicles with an manual transmission/gasoline engine combination, GO to X6.
For all other transmission/engine combinations, REPAIR circuit CLS28 (BU/WH) for a short to ground. TEST the system for normal operation.
No
For vehicles with an automatic transmission/gasoline engine combination, GO to X7.
For vehicles with an automatic transmission/diesel engine combination, GO to X8.
For vehicles with a manual transmission, INSTALL a new reversing lamp switch. TEST the system for normal operation.
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X6 ISOLATE THE PCM AS THE CAUSE OF THE SHORT TO GROUND (MANUAL TRANSMISSION, GASOLINE ENGINE)
- Ignition OFF.
- Disconnect: PCM C175b.
- Ignition ON.
- Do the reversing lamps continue to illuminate?
Yes
REPAIR circuit CLS28 (BU/WH) for a short to ground. TEST the system for normal operation.
No
GO to X7.
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X7 CHECK FOR CORRECT PCM OPERATION
- Disconnect all the PCM connectors.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect all the PCM connectors and make sure they seat correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new PCM. REFER to Computers and Control Systems. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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X8 CHECK FOR CORRECT TCM OPERATION
- Disconnect the TCM connector.
- Check for:
- corrosion
- damaged pins
- pushed-out pins
- Connect the TCM connector and make sure it seats correctly.
- Operate the system and verify the concern is still present.
- Is the concern still present?
Yes
INSTALL a new TCM. REFER to Automatic Transmission/Transaxle &/or Transmission Control Systems. TEST the system for normal operation.
No
The system is operating correctly at this time. The concern may have been caused by a loose or corroded connector.
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