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Electronic Control System Gas Plus Engines – FAULT CODE 591

Exhaust Back Pressure Sensor Circuit – Shorted High

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Overview

CODE REASON EFFECT
Fault Code: 591
PID: S034
SPN: 648
FMI: 3
LAMP: Amber
SRT: 

Exhaust Back Pressure Sensor Circuit – Shorted High. High voltage detected at the exhaust back pressure pin of the ECM connector.

Possible reduced performance.

Exhaust Back Pressure Sensor Circuit
SMALL | MEDIUM | LARGE

Circuit Description

The electronic control module (ECM) uses this sensor’s input to determine the pressure of the exhaust gas, which affects the fueling of the engine.

Component Location

The exhaust back pressure sensor is located above the rocker housing and is connected to the closed-crankcase ventilation filter bracket. The sensor utilizes a tube that is fitted into the exhaust outlet connection.
Refer to Procedure 100-002 (Engine Diagrams) in Section E for a detailed component location view.

Shop Talk

The exhaust back pressure sensor tube is vulnerable to the collection of condensation and sludge. Periodic maintenance of this tube should be performed. This sensor is located such that it is protected from extreme heat. Do
not relocate this sensor from its on-engine position.

On the L Gas Plus engine an OEM tube from the exhaust connects to an accumulator on the exhaust side of the engine. A tube then connects the accumulator to the exhaust back pressure sensor.

Cautions and Warnings

 CAUTION 

To reduce the possibility of damaging a new ECM, all other active fault codes must be investigated prior to replacing the ECM.
 CAUTION 

To reduce the possibility of pin and harness damage, use the following test leads when taking a measurement:
Part Number 3822758 – male Deutsch™/AMP™/Metri-Pack™ test lead
Part Number 3824775 – breakout cable.

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Check the fault codes.  
  STEP 1A. Check for Fault Code 2185. Fault Code 2185 active?
  STEP 1B. Check for an inactive fault code. Fault Code 591 inactive?
STEP 2. Check the exhaust back pressure sensor and circuit.  
  STEP 2A. Inspect the exhaust back pressure sensor and connector pins. Dirty or damaged pins?
  STEP 2B. Check the circuit response. Fault Code 592 active and Fault Code 591 inactive?
  STEP 2C. Check the sensor supply voltage and return circuit. 4.5 to 5.25-VDC?
  STEP 2D. Check the fault codes and verify sensor condition. Fault Code 591 active?
STEP 3. Check the ECM and engine harness.  
  STEP 3A. Inspect the ECM and engine harness connector pins. Dirty or damaged pins?
  STEP 3B. Check for an open circuit in the engine harness. Less than 10 ohms?
  STEP 3C. Check for a pin to pin short circuit from in the engine harness. Greater than 100k ohms?
  STEP 3D. Check for a pin-to-pin short circuit from in the engine harness. Greater than 100k ohms?
  STEP 3E. Check for an inactive fault code. Fault Code 591 inactive?
STEP 4. Clear the fault codes.  
  STEP 4A. Disable the fault code. Fault Code 591 inactive?
  STEP 4B. Clear the inactive fault codes. All fault codes cleared?

Guided Step 1 – Check the fault codes.

Guided Step 1A – Check for Fault Code 2185.

Conditions

  • Turn keyswitch ON
  • Connect the INSITE™ electronic service tool.

Action

Check for sensor supply fault codes.

Use INSITE™ electronic service tool to read the fault codes.

Fault Code 2185 active?
YES NO
No Repair No Repair
Fault Code 2185

Guided Step 1B – Check for an inactive fault code.

Conditions

  • Turn keyswitch ON
  • Connect the INSITE™ electronic service tool.

Action

Check for an inactive fault code.

Use INSITE™ electronic service tool to read the fault codes.

Fault Code 591 inactive?
YES NO
No Repair No Repair

Guided Step 2 – Check the exhaust back pressure sensor and circuit.

Guided Step 2A – Inspect the exhaust back pressure sensor and connector pins.

Conditions

  • Turn keyswitch OFF
  • Disconnect the exhaust back pressure sensor from the engine harness.

Action

Inspect the engine harness and exhaust back pressure sensor connector pins for the following:

  • Loose connector
  • Corroded pins
  • Bent or broken pins
  • Pushed back or expanded pins
  • Moisture in or on the connector
  • Missing or damaged connector seals
  • Dirt or debris in or on the connector pins
  • Connector shell broken
  • Wire insulation damage
  • Damaged connector locking tab.

For general inspection techniques, refer to Procedure 019-361 (Component Connector and Pin Inspection) in Section 19.

Dirty or damaged pins?
YES NO

A damaged connection has been detected in the sensor or harness connector.

Repair the damaged pins. Repair or replace the engine harness or replace the sensor, whichever has the damaged pins.

 No Repair

Guided Step 2B – Check the circuit response.

Conditions

  • Turn keyswitch OFF
  • Disconnect the exhaust back pressure sensor from the engine harness
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

Check for the appropriate circuit response after 30 seconds.

  • Use INSITE™ electronic service tool to read the fault codes.

Fault Code 592 active and Fault Code 591 inactive?
YES NO
No Repair No Repair

Guided Step 2C – Check the sensor supply voltage and return circuit.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the exhaust back pressure sensor
  • Turn keyswitch ON.

Action

Check the supply voltage and return circuit.

  • Measure the supply voltage between 5 Volt SUPPLY pin and the exhaust back pressure RETURN pin at the exhaust back pressure sensor connector of the engine harness.

Refer to the circuit diagram or wiring diagram for connector pin identification.

4.5 to 5.25-VDC?
YES NO
No Repair No Repair

Guided Step 2D – Check the fault codes and verify sensor condition.

Conditions

  • Turn keyswitch OFF
  • Connect the exhaust back pressure sensor to the engine harness.
  • Turn keyswitch ON
  • Connect INSITE™ electronic service tool.

Action

Check for the appropriate circuit response after 30 seconds.

  • Use INSITE™ electronic service tool to read the fault codes.

Fault Code 591 active?
YES NO

A damaged sensor has been detected.

Replace the exhaust back pressure sensor.
Refer to 019-347 (Exhaust Back Pressure Sensor) in Section 19.

No Repair

Guided Step 3 – Check the ECM and engine harness.

Guided Step 3A – Inspect ECM and engine harness connector pins.

Conditions

  • Turn keyswitch OFF
  • Disconnect engine harness from the ECM.

Action

Inspect the engine harness and ECM connector pins for the following:

  • Loose connector
  • Corroded pins
  • Bent or broken pins
  • Pushed back or expanded pins
  • Moisture in or on the connector
  • Missing or damaged connector seals
  • Dirt or debris in or on the connector pins
  • Connector shell broken
  • Wire insulation damage
  • Damaged connector locking tab.

For general inspection techniques, refer to Procedure 019-361 (Component Connector and Pin Inspection) in Section 19.

Dirty or damaged pins?
YES NO

A damaged connection has been detected in the ECM connector or engine harness connector.

Repair the damaged pins. Repair or replace the engine harness, or replace the ECM whichever has the damaged pins.

 No Repair

Guided Step 3B – Check for an open circuit in the engine harness.

Conditions

  • Turn keyswitch OFF
  • Disconnect the engine harness from the ECM.
  • Disconnect the exhaust back pressure sensor from the engine harness.

Action

Check for an open circuit.

  • Measure the resistance between the ECM connector 1 RETURN pin and the exhaust back pressure sensor connector RETURN pin.

Refer to the circuit diagram or wiring diagram for connector pin identification.

Refer to Procedure 019-360 (Resistance Measurements Using a Multimeter) in Section 19, for general resistance measurement techniques.

Less than 10 ohms?
YES NO
No Repair

An open return circuit has been detected in the engine harness.

Repair the damaged pins. Repair or replace the engine harness.

Guided Step 3C – Check for a pin-to-pin short circuit in the engine harness.

Conditions

  • Turn keyswitch OFF
  • Disconnect engine harness from the ECM.
  • Disconnect the exhaust back pressure sensor from the engine harness.

Action

Check for a pin to pin short.

  • Measure the resistance between the exhaust back pressure SIGNAL pin in engine harness connector 2 and all other pins in engine connector 2.
  • Measure the resistance from the exhaust back pressure SIGNAL pin in engine harness connector 2 to all pins in engine connector 1.

Refer to the circuit diagram or wiring diagram for connector pin identification.

Refer to Procedure 019-360 (Resistance Measurements Using a Multimeter) in Section 19, for general resistance measurement techniques.

SMALL | MEDIUM | LARGE

Greater than 100k ohms?
YES NO
No Repair

A pin-to-pin short circuit on the SIGNAL line has been detected in the engine harness.

Repair the damaged pins. Repair or replace the engine harness.

Guided Step 3D – Check for a pin-to-pin short circuit in the engine harness.

Conditions

  • Turn keyswitch OFF
  • Disconnect engine harness from the ECM.
  • Disconnect the exhaust back pressure sensor from the engine harness.

Action

Check for a pin-to-pin short.

  • Measure the resistance between the exhaust back pressure sensor 5 Volt SUPPLY pin in engine harness connector 1 and all other pins in ECM connector 1.
  • Measure the resistance from the exhaust back pressure sensor 5 Volt SUPPLY pin in engine harness connector 1 and all pins in ECM connector 2.

Refer to the circuit diagram or wiring diagram for connector pin identification.

Refer to Procedure 019-360 (Resistance Measurements Using a Multimeter) in Section 19, for general resistance measurement techniques.

Greater than 100k ohms?
YES NO
No Repair

A pin-to-pin short circuit on the SUPPLY line has been detected in the engine harness.

Repair the damaged pins. Repair or replace the engine harness.

Guided Step 3E – Check for an inactive fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect the INSITE™ electronic service tool.

Action

Check for the appropriate circuit response after 30 seconds.

Use INSITE™ electronic service tool to read the fault codes.

Fault Code 591 inactive?
YES NO
No Repair

Guided Step 4 – Clear the fault codes.

Guided Step 4A – Disable the fault code.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect the INSITE™ electronic service tool.

Action

Disable the fault code.

  • Start the engine and let it idle for 1 minute.
  • Use INSITE™ electronic service tool to verify the fault code is inactive.

Fault Code 591 inactive?
YES NO
No Repair

Return to the troubleshooting steps or contact a Cummins® Authorized Repair Location if all steps have been completed and checked again.

Guided Step 4B – Clear the inactive fault codes.

Conditions

  • Connect all components
  • Turn keyswitch ON
  • Connect the INSITE™ electronic service tool.

Action

Clear the inactive fault codes.

  • Use INSITE™ electronic service tool to clear the inactive fault codes.

All fault codes cleared?
YES NO
No Repair

Troubleshoot any remaining active fault codes.
Repair complete
Appropriate troubleshooting charts
Last Modified:  04-Apr-2008
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