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FAULT CODE 434

Unswitched Battery Supply Circuit

Overview

CODE REASON EFFECT
Fault Code: 434
PID: S251
SPN: 627
FMI: 4
LAMP: Yellow
SRT: 00-614

Battery voltage at pins 20, 21, 22, and 23 of actuator harness connector (relative to return pins 9, 25, and 27 of the actuator harness connector) fell below 6.2 VDC for a fraction of a second or electronic control module (ECM) was not allowed to power down correctly (retain the battery supply voltage for 3 seconds) after keyswitch OFF.

Possibly no noticeable performance effects or possibility of the engine dying or difficulty in starting the engine.

Unswitched Battery Supply
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Circuit Description

The ECM receives constant voltage from the batteries through the unswitched battery wires that are connected directly to the positive (+) battery post. There are two in-line 10-amp fuses in the unswitched battery wires to protect the actuator harness from overheating. The ECM receives switched battery input through the vehicle keyswitch wire when the vehicle keyswitch is turned ON. The battery return wires are connected directly to the negative (-) battery post.

Component Location

The ECM is connected to the battery by the actuator harness. This direct link provides a constant power supply for the ECM. The location of the battery will vary with the OEM. Refer to the OEM manual.

Shop Talk

  • Examine the injector pigtail nuts, and make sure they are tightened down to the proper torque. Confirm that the pigtail nuts and solenoid posts do not have damaged threads.
  • If the ECM unswitched battery supply is taken from the starter, check for low voltage during cranking. Low voltage during cranking can cause the ECM power supply to drop below specifications and log Fault Code 434.
  • Optimally, the unswitched battery supply for the ECM will be wired directly to the battery.

Cautions and Warnings

 WARNING 

The injector solenoids receive high voltage when the engine is operating. To reduce the possibility of personal injury from electrical shock, do not wear jewelry or damp clothing, and do not touch the injector solenoids or the solenoid wires when the engine is operating.
 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 3823995 – male Weather-Pack test lead.
 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 lead when taking a measurement:
Part Number 3823995 – male Weather-Pack test lead.
 CAUTION 

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

Troubleshooting Steps

STEPS SPECIFICATIONS
STEP 1. Read the fault codes.  
  STEP 1A. Read the fault code. No active or inactive injector fault codes
STEP 2. Check the batteries and the power connector.  
  STEP 2A. Inspect the 3-pin power connector. No damaged pins or loose connections
  STEP 2B. Check the resistance of the battery supply circuit. Less than 10 ohms
  STEP 2C. Check the battery voltage. Normal conditions: At least 12 VDC, during cranking: minimum 6.2 VDC
  STEP 2D. Check the battery. Connections are tight and corrosion free
STEP 3. Check the two 10-amp fuses.  
  STEP 3A. Check if the two 10-amp fuses are installed correctly. Fuses installed correctly
  STEP 3B. Check if the two 10-amp fuses are blown. Fuses not blown
STEP 4. Check the actuator harness.  
  STEP 4A. Inspect the harness and the ECM connector pins. No damaged pins
  STEP 4B. Check for an open circuit in the battery power circuits. 10 to 15 VDC
  STEP 4C. Check for a short circuit in the battery return wires. More than 100k ohms
  STEP 4D. Check the add-on or the accessory wiring at positive (+) terminal of the battery. No damaged wires
  STEP 4E. Check for good vehicle grounds. Meets OEM specifications for voltage drop under electrical load
  STEP 4F. Check the injector solenoid captive nuts for proper torque. Captive nuts are correctly tightened
STEP 5. Clear the fault codes.  
  STEP 5A. Disable the fault code. Fault Code 434 inactive
  STEP 5B. Clear the inactive fault codes. All fault codes cleared

Guided Step 1 – Read the fault codes.

Guided Step 1A – Read the fault code.

Conditions

  • Turn keyswitch ON.

Action

  • Read the fault codes using INSITE™.
OK NOT OK

No active or inactive injector fault codes

Troubleshoot the injector fault codes. Refer to the appropriate injector fault code tree.

Guided Step 2 – Check the batteries and the power connector.

Guided Step 2A – Inspect the 3-pin power connector.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the actuator harness from the battery at the 3-pin connector.

Action

  • Bent or broken pins
  • Pushed back or expanded pins
  • Corroded pins
  • Moisture in or on the connector
  • Missing or damaged seals.
OK NOT OK

No damaged pins or loose connections

Repair the 3-pin connector. Refer to Procedure 019-201 or 019-202.

 CAUTION 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3823995 – male Weather-Pack test lead.
Guided Step 2B – Check the resistance of the battery supply circuit.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the actuator harness from the battery at the 3-pin connector.

Action

  • Measure the resistance from pin A to the positive (+) battery terminal.
  • Measure the resistance from pin C to the positive (+) battery terminal.
  • Measure the resistance from pin B to the negative (-) battery terminal.
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OK NOT OK

Less than 10 ohms

Repair or replace the power harness. Refer to the OEM troubleshooting and repair manual.

Guided Step 2C – Check the battery voltage.

Conditions

  • Turn keyswitch ON.

Action

  • Place positive (+) probe of the multimeter on the positive battery terminal, and touch negative (-) probe to the negative battery terminal while trying to start engine.
SMALL | MEDIUM | LARGE
OK NOT OK

Normal conditions: 12 VDC, during cranking: minimum 6.2 VDC

Charge or replace the battery. Refer to the OEM troubleshooting and repair manual.

Guided Step 2D – Check the battery.

Conditions

  • Turn keyswitch OFF.

Action

  • Check the battery terminal connections on both positive (+) and negative (-) terminals.
OK NOT OK

Connections are tight and corrosion free

Tighten the loose connections, and clean the terminals. Refer to the OEM troubleshooting and repair manual.

Guided Step 3 – Check the two 10-amp fuses.

Guided Step 3A – Check if the two 10-amp fuses are installed correctly.

Conditions

  • Turn keyswitch OFF.

Action

  • Inspect the two 10-amp fuses for correct installation.
SMALL | MEDIUM | LARGE
OK NOT OK

Fuses installed correctly

Install the fuses correctly. Refer to Procedure 019-198.

Guided Step 3B – Check if the two 10-amp fuses are blown.

Conditions

  • Turn keyswitch OFF.

Action

  • Inspect the two 10-amp fuses to see if they are blown.
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OK NOT OK

Fuses not blown

Locate the short circuit.

  • Replace the actuator harness. Refer to Procedure 019-043.
  • Replace the blown fuse(s).

Guided Step 4 – Check the actuator harness.

 CAUTION 

To reduce the possibility of damaging a new ECM, all other active fault codes must be investigated prior to replacing the ECM.
Guided Step 4A – Inspect the harness and the ECM connector pins.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the actuator harness connector from the ECM.

Action

  • Bent or broken pins
  • Pushed back or expanded pins
  • Corroded pins
  • Moisture in or on the connector
  • Missing or damaged seals.
OK NOT OK

No damaged pins

Repair the damaged pins.

  • Flush the dirt, debris, or moisture from the connector pins using electronic contact cleaner, Part Number 3824510.
  • Repair the actuator harness. Refer to Procedure 019-203.
  • Replace the actuator harness. Refer to Procedure 019-043.
  • Replace the ECM. Refer to Procedure 019-031.
  • Replace the o-ring on the 28-pin connector if it is damaged or missing. Refer to Procedure 019-203.

 CAUTION 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3822758 – male Deutsch/AMP/Metri-Pack test lead.
Guided Step 4B – Check for an open circuit in the battery power circuits.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the actuator harness connector from the ECM.

Action

  • Measure the voltage from pin 20 to pin 9 of the actuator harness.
  • Measure the voltage from pin 21 to pin 25 of the actuator harness.
  • Measure the voltage from pin 22 to pin 27 of the actuator harness.
  • Measure the voltage from pin 23 to pin 9 of the actuator harness.
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OK NOT OK

10 to 15 VDC

Repair or replace the actuator harness.

  • Repair the actuator harness. Refer to Procedure 019-203.
  • Replace the actuator harness. Refer to Procedure 019-043.

 CAUTION 

To reduce the possibility of pin and harness damage, use the following test lead when taking a measurement:
Part Number 3822758 – male Deutsch/AMP/Metri-Pack test lead.
Guided Step 4C – Check for a short circuit in the battery return wires.

Conditions

  • Turn keyswitch OFF.
  • Disconnect the actuator harness to the 3-pin battery connector.
  • Disconnect the actuator harness connector from the ECM.

Action

  • Measure the resistance from pin 20 of the actuator harness connector to all the other pins in the connector, except pin 21.
  • Measure the resistance from pin 21 of the actuator harness connector to all the other pins in the connector, except pin 20.
  • Measure the resistance from pin 22 of the actuator harness connector to all the other pins in the connector, except pin 23.
  • Measure the resistance from pin 23 of the actuator harness connector to all the other pins in the connector, except pin 22.
SMALL | MEDIUM | LARGE
OK NOT OK

More than 100k ohms

Replace the actuator harness. Refer to Procedure 019-043.

Guided Step 4D – Check the add-on or accessory wiring at positive (+) terminal of the battery.

Conditions

  • Turn keyswitch OFF.

Action

  • Starting at the positive (+) terminal of the battery, follow any add-on or accessory wiring, and examine wire(s) for damaged insulation or an installation error that can cause the supply wire to be shorted to the engine block.
OK NOT OK

No damaged wires

Repair or replace the damaged wiring.

Guided Step 4E – Check for good vehicle grounds.

Conditions

  • Turn keyswitch OFF.

Action

  • Check from negative (-) battery post to block ground.
  • Check from block ground to negative (-) starter post ground.
  • Check block to frame ground.
  • Check block to cab ground.
OK NOT OK

Meets OEM specifications for voltage drop under electrical load

Repair vehicle grounds.

 WARNING 

The injector solenoids receive high voltage when the engine is operating. To reduce the possibility of personal injury from electrical shock, do not wear jewelry or damp clothing, and do not touch the injector solenoids or the solenoid wires when the engine is operating.
Guided Step 4F – Check the injector solenoid captive nuts for proper torque.

Conditions

  • Turn keyswitch OFF.

Action

  • Remove the valve covers and check the injector solenoid captive nuts for proper torque.
SMALL | MEDIUM | LARGE
OK NOT OK

Captive nuts are correctly tightened

Tighten the captive nuts. Replace the valve covers.

Guided Step 5 – Clear the fault codes.

Guided Step 5A – Disable the fault code.

Conditions

  • Connect all the components.

Action

  • Start the engine and let it idle for 1 minute.
  • Verify Fault Code 434 is inactive.
OK NOT OK

Fault Code 434 inactive

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

Guided Step 5B – Clear the inactive fault codes.

Conditions

  • Connect all the components.

Action

  • Erase the inactive fault codes using INSITE™.
OK NOT OK

All fault codes cleared

Troubleshoot any remaining active fault codes.
Repair complete
Appropriate troubleshooting chart
Last Modified:  29-Oct-2003
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Published by Jack

Hello, I'm Jack, a diesel engine fan and a blogger. I write about how to fix and improve diesel engines, from cars to trucks to generators. I also review the newest models and innovations in the diesel market. If you are interested in learning more about diesel engines, check out my blog and leave your feedback.