DEF Controller Resistor - Test
Use this procedure to troubleshoot a problem with the DEF controller resistor.
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| J1939 Code and Description | CDL Code and Description | Comments |
|---|---|---|
| 7602–2
Aftertreatment #1 DEF Controller #1 Identification : Erratic, Intermittent, or Incorrect |
5028–2
Aftertreatment #1 DEF Controller #1 Identification : Erratic, Intermittent, or Incorrect |
The Aftertreatment #1 Diesel Exhaust Fluid Control Unit (DCU) #1 has detected a resistance outside the normal resistance of the DCU resistor. |
| 7602–3
Aftertreatment #1 DEF Controller #1 Identification : Voltage Above Normal |
5028–3
Aftertreatment #1 DEF Controller #1 Identification : Voltage Above Normal |
The Aftertreatment #1 DCU #1 has detected an open circuit in the DCU resistor circuit. |
| 7602–4
Aftertreatment #1 DEF Controller #1 Identification : Voltage Below Normal |
5028–4
Aftertreatment #1 DEF Controller #1 Identification : Voltage Below Normal |
The Aftertreatment #1 DCU #1 has detected a short circuit in the DCU resistor circuit. |
| 7603–2
Aftertreatment #1 DEF Controller #2 Identification : Erratic, Intermittent, or Incorrect |
5029–2
Aftertreatment #1 DEF Controller #2 Identification : Erratic, Intermittent, or Incorrect |
The Aftertreatment #1 DCU #2 has detected a resistance outside the normal resistance of the DCU resistor. |
| 7603–3
Aftertreatment #1 DEF Controller #2 Identification : Voltage Above Normal |
5029–3
Aftertreatment #1 DEF Controller #2 Identification : Voltage Above Normal |
The Aftertreatment #1 DCU #2 has detected an open circuit in the DCU resistor circuit. |
| 7603–4
Aftertreatment #1 DEF Controller #2 Identification : Voltage Below Normal |
5029–4
Aftertreatment #1 DEF Controller #2 Identification : Voltage Below Normal |
The Aftertreatment #1 DCU #2 has detected a short circuit in the DCU resistor circuit. |
| 7604–2
Aftertreatment #2 DEF Controller #1 Identification : Erratic, Intermittent, or Incorrect |
5030–2
Aftertreatment #2 DEF Controller #1 Identification : Erratic, Intermittent, or Incorrect |
The Aftertreatment #2 DCU #1 has detected a resistance outside the normal resistance of the DCU resistor. |
| 7604–3
Aftertreatment #2 DEF Controller #1 Identification : Voltage Above Normal |
5030–3
Aftertreatment #2 DEF Controller #1 Identification : Voltage Above Normal |
The Aftertreatment #2 DCU #1 has detected an open circuit in the DCU resistor circuit. |
| 7604–4
Aftertreatment #2 DEF Controller #1 Identification : Voltage Below Normal |
5030–4
Aftertreatment #2 DEF Controller #1 Identification : Voltage Below Normal |
The Aftertreatment #2 DCU #1 has detected a short circuit in the DCU resistor circuit. |
| 7605–2
Aftertreatment #2 DEF Controller #2 Identification : Erratic, Intermittent, or Incorrect |
5031–2
Aftertreatment #2 DEF Controller #2 Identification : Erratic, Intermittent, or Incorrect |
The Aftertreatment #2 DCU # 2 has detected a resistance outside the normal resistance of the DCU resistor. |
| 7605–3
Aftertreatment #2 DEF Controller #2 Identification : Voltage Above Normal |
5031–3
Aftertreatment #2 DEF Controller #2 Identification : Voltage Above Normal |
The Aftertreatment #2 DCU #2 has detected an open circuit in the DCU resistor circuit. |
| 7605–4
Aftertreatment #2 DEF Controller #2 Identification : Voltage Below Normal |
5031–4
Aftertreatment #2 DEF Controller #2 Identification : Voltage Below Normal |
The Aftertreatment #2 DCU #2 has detected a short circuit in the DCU resistor circuit. |
- Codes
- DCU resistor
- Wiring
- Tests
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| |
| Illustration 1 | g06066684 |
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| Troubleshooting Test Step | Value | Result |
|---|---|---|
1. Check for Codes A. Establish communication between Cat® Electronic Technician (ET) and the Electronic Control Module (ECM). Refer to Troubleshooting, Electronic Service Tools if necessary. B. Turn the keyswitch to ON. C. Look for an active or logged code. |
Codes |
Result: No codes are present. Proceed to Test Step 7. Result: There are codes present. Proceed to Test Step 2. |
2. Check the Resistance of the DCU Resistor A. Turn the keyswitch to OFF. B. Disconnect the 86-pin connector from the DCU that is logging the code. C. Measure the resistance between pin-38 and pin-39 on the DCU that is logging the code. - For Aftertreatment #1 DCU #1 the resistance should be 178Ω ± 10Ω - For Aftertreatment #2 DCU #2 the resistance should be 604Ω ± 10Ω - For Aftertreatment #2 DCU #1 the resistance should be 1540Ω ± 10Ω - For Aftertreatment #2 DCU #2 the resistance should be 5230Ω ± 10Ω Note: The 398-5063 Probe must be used to prevent damage to the DCU connector. |
DCU Resistor |
Result: The resistance measurement of the DCU resistor at the suspect DCU connector was OK. Proceed to Test Step 7. Result: The resistance measurement of the DCU resistor at the suspect DCU connector was NOT OK. Proceed to Test Step 3. |
3. Check the Resistance of the Diesel Exhaust Fluid Resistor A. Turn the keyswitch to OFF. B. Disconnect the 8-pin connector from the affected DCU. C. Measure the resistance between the following on the DCU resistor pins: - For Aftertreatment #1 DCU #1, pin-1 and pin-5, the resistance should measure 178Ω ± 10Ω - For Aftertreatment #1 DCU #2, pin-2 and pin-6, the resistance should measure 604Ω ± 10Ω - For Aftertreatment #2 DCU #1, pin-3 and pin-7, the resistance should measure 1540Ω ± 10Ω - For Aftertreatment #2 DCU #2, pin-4 and pin-8, the resistance should measure 5230Ω ± 10Ω |
Resistance |
Result: The resistance measurement of the DCU resistor was within specifications. Proceed to Test Step 4. Result: The resistance measurement of the DCU resistor was not within specifications. A failed DCU resistor has been detected. Repair: Replace the DCU resistor. Proceed to Test Step 7. |
4. Check the Wiring Between the DCU Resistor and the Suspect DCU for an Open Circuit A. Turn the keyswitch to OFF. B. Disconnect the 86-pin connector from the suspect DCU. C. Disconnect the 8-pin connector from the DCU resistor. D. Measure the resistance between the following pins on the suspect DCU: - For Aftertreatment #1 DCU #1, pin-38 on the 86-pin DCU connector and pin-1 on the DCU resistor 8-pin connector - For Aftertreatment #1 DCU #1, pin-39 on the 86-pin DCU connector and pin-5 on the DCU resistor 8-pin connector - For Aftertreatment #1 DCU #2, pin-38 on the 86-pin DCU connector and pin-2 on the DCU resistor 8-pin connector - For Aftertreatment #1 DCU #2, pin-39 on the 86-pin DCU connector and pin-6 on the DCU resistor 8-pin connector - For Aftertreatment #2 DCU #1, pin-38 on the 86-pin DCU connector and pin-3 on the DCU resistor 8-pin connector - For Aftertreatment #2 DCU #1, pin-39 on the 86-pin DCU connector and pin-7 on the DCU resistor 8-pin connector - For Aftertreatment #2 DCU #2, pin-38 on the 86-pin DCU connector and pin-4 on the DCU resistor 8-pin connector - For Aftertreatment #2 DCU #2, pin-39 on the 86-pin DCU connector and pin-8 on the DCU resistor 8-pin connector Note: The 398-5063 Probe must be used to prevent damage to the DCU connector. |
Ohms |
Result: There was less than 10Ω of resistance between all the pins on the suspect DCU connector and the DCU resistor. Proceed to Test Step 5. Result: There was more than 10Ω of resistance between all the pins on the suspect DCU connector and the DCU resistor. An open circuit has been detected. Repair: Replace the wiring harness. Proceed to Test Step 7. |
5. Check the Wiring Between the DCU Resistor and the Suspect DCU for a Short Circuit A. Turn the keyswitch to OFF. B. Disconnect the 86-pin connector from the suspect DCU. C. Disconnect the 8-pin connector from the DCU resistor. D. Measure the resistance between the following points: - For Aftertreatment #1 DCU #1 measure the resistance between pin 1 on the DCU resistor 8-pin connector and a known good ground. - For aftertreatment #1 DCU #1 measure the resistance between pin 5 on the DCU resistor 8-pin connector and a known good ground. - For aftertreatment #1 DCU #2 measure the resistance between pin 2 on the DCU resistor 8-pin connector and a known good ground. - For aftertreatment #1 DCU #2 measure the resistance between pin 6 on the DCU resistor 8-pin connector and a known good ground. - For aftertreatment #2 DCU #1 measure the resistance between pin 3 on the DCU resistor 8-pin connector and a known good ground. - For aftertreatment #2 DCU #1 measure the resistance between pin 7 on the DCU resistor 8-pin connector and a known good ground. - For aftertreatment #2 DCU #2 measure the resistance between pin 4 on the DCU resistor 8-pin connector and a known good ground. - For aftertreatment #2 DCU #2 measure the resistance between pin 8 on the DCU resistor 8-pin connector and a known good ground. |
Ohms |
Result: There was more than 100KΩ of resistance between all the pins on the suspect DCU and the DCU resistor. Proceed to Test Step 6. Result: There was less than 100KΩ of resistance between all the pins on the suspect DCU and the DCU resistor. A short circuit has been detected. Repair: Replace the wiring harness. Proceed to Test Step 7. |
6. Check the Wiring Between the DCU Resistor and the Suspect DCU for a Pin to Pin Short Circuit A. Turn the keyswitch to OFF. B. Disconnect the 86-pin connector from the suspect DCU. C. Disconnect the 8-pin connector from the DCU resistor. D. Measure the resistance between the following pins on the suspect DCU: - Measure the resistance between pin 38 on the DCU 86-pin connector and all other pins in the DCU wiring harness connector. - Measure the resistance between pin 39 on the DCU resistor 8-pin connector all other pins in the DCU wiring harness connector. |
Ohms |
Result: There were more than 100 K ohms of resistance between all the pins on the suspect DCU wiring harness connector. Proceed to Test Step 7. Result: There were less than 100 K ohms of resistance between all the pins on the suspect DCU wiring harness connector. A short circuit has been detected. Repair: Replace the wiring harness. Proceed to Test Step 7. |
7. Perform the "Aftertreatment Dosing System Functional Test" A. Turn the keyswitch to ON. Do not start the engine. B. Connect to the "Selective Catalyst Reduction System" in Cat ET. C. Perform the "Aftertreatment Dosing System Functional Test" to pressurize the system. |
"Aftertreatment Dosing System Functional Test" |
Result: The test is successful. Return the unit to service. Result: The test is not successful. Repair: Troubleshoot any additional codes. Refer to the Troubleshooting manual for the correct procedure. |
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