The Suspect Parameter Number (SPN) 807, labeled as “Dif 2 – ASR Valve,” is a critical component in the vehicle’s Anti-Slip Regulation (ASR) system, commonly referred to as traction control. This parameter is instrumental in monitoring the function of the ASR valve, which regulates brake pressure to prevent wheel slip during acceleration. It is particularly prevalent in heavy-duty trucks and buses, especially those equipped with drivetrains from manufacturers like Mercedes-Benz, Bosch, and Volvo. Understanding this SPN is crucial for diagnostics as it plays a vital role in vehicle stability and safety. Proper functioning of the ASR system helps maintain traction under various driving conditions, reducing the risk of skidding and improving vehicle control.
Technical Overview
The engineering behind the Dif 2 – ASR Valve involves the Electronic Control Module (ECM) monitoring the operation of the ASR valve, which is either a solenoid-driven hydraulic valve or an electronically controlled pneumatic valve. The ECM receives data through a combination of sensor inputs and actuator outputs. Typically, this parameter is monitored via a digital signal transmitted over the Controller Area Network (CAN) bus. The data might be received from a wheel speed sensor or a dedicated ASR pressure sensor, which feeds information to the ECM. The normal operating range for this parameter depends on the specific calibration settings defined by the vehicle manufacturer but usually involves maintaining brake pressure within predefined limits to optimize traction without causing excessive brake wear or thermal damage.
J1939 Network Behavior
In the SAE J1939 network, the SPN 807 is transmitted as part of a Parameter Group Number (PGN) that is specific to the vehicle manufacturer’s network configuration. Typically, this data is broadcast at a regular interval, often several times per second, to ensure real-time traction control adjustments. The source address for this SPN is usually associated with the traction control unit or the brake control module. Other Electronic Control Units (ECUs) on the network, like the engine or transmission control modules, may utilize this data to optimize power delivery and ensure coordinated vehicle dynamics, especially under challenging driving conditions. The precise PGN and transmission rate can vary by manufacturer, with some using a proprietary PGN structure to encapsulate this information.
Diagnostic Importance
The diagnostic importance of SPN 807 cannot be overstated, as faults in the ASR system can lead to compromised vehicle safety. When the ECM detects an anomaly with the ASR valve, it may trigger a fault code that activates warning lights on the dashboard and possibly limits vehicle acceleration or engine power as a protective measure. Ignoring these fault codes can lead to reduced traction control effectiveness, increasing the likelihood of wheel slip and potential loss of vehicle control. In severe cases, it may also lead to increased brake wear or damage due to inappropriate pressure regulation. Therefore, timely diagnosis and resolution of any issues related to this SPN are essential to maintain vehicle safety and performance.
Common Failure Patterns
Technicians often encounter several common failure patterns associated with SPN 807. Wiring issues, such as chafed or corroded connectors, are frequent culprits that can lead to intermittent or complete signal loss. Sensor degradation, particularly in harsh environments, can also lead to inaccurate readings or failure. Contamination of the ASR valve with debris or moisture can affect its mechanical operation, leading to sluggish or erratic performance. Calibration drift, due to software updates or sensor aging, may cause the system to operate outside normal parameters. Mechanical failures, such as valve sticking or solenoid burnout, are other potential issues that technicians must be prepared to diagnose and repair.
Diagnostic Approach
To effectively diagnose issues related to SPN 807, technicians should begin with a comprehensive visual inspection of the ASR system components, checking for obvious signs of damage or wear. Diagnostic tools such as a multimeter or an oscilloscope may be necessary to check the electrical integrity of the circuit, including voltage and continuity tests. Reference values for these checks can usually be found in the vehicle’s service manual or OEM documentation. In cases where the issue is not immediately apparent, advanced diagnostic software, such as those provided by Cummins or Bosch, can be employed to perform deeper system analysis and recalibration. If the fault persists despite following these procedures, it may be necessary to escalate the issue to OEM-specific diagnostic software, which can provide detailed insights and facilitate advanced troubleshooting steps, including reprogramming or component replacement protocols.
Fault Codes for SPN 807
FMI 0: Data valid but above normal operational range (most severe)
SPN 807 FMI 0 indicates the differential lock ASR (Anti-Slip Regulation) valve signal exceeds normal operational parameters. This fault commonly appears during aggressive terrain operations when the traction control system experiences hydraulic pressure spikes or electrical overcurrent conditions. T
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FMI 1: Data valid but below normal operational range (most severe)
SPN 807 FMI 1 indicates the differential brake valve (ASR) solenoid circuit reports voltage below the normal operational range. This fault often appears after a control module replacement when technicians forget to recalibrate the valve, or following a wiring repair where a crimp connector introduce
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FMI 2: Data erratic, intermittent or incorrect
SPN 807 FMI 2 relates to the ASR (Anti-Slip Regulation) valve, indicating erratic or incorrect data. This fault often surfaces after a vehicle experiences unstable traction scenarios, such as during heavy rain or on icy roads. Commonly, technicians find this code following a wheel speed sensor or AB
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FMI 3: Voltage above normal or shorted high
The SPN 807 FMI 3 fault refers to an issue with the Dif 2 – ASR Valve, where the voltage is above normal or shorted high. This fault code commonly appears following repairs or replacements involving the wiring harness, particularly if the ASR valve connections are not correctly reattached. In practi
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FMI 4: Voltage below normal or shorted low
SPN 807 FMI 4 indicates the Anti-Slip Regulation (ASR) valve control circuit experiencing voltage below normal threshold or short-to-ground condition. This fault commonly occurs in Mercedes-Benz Actros and MAN TGX vehicles after wheel speed sensor replacement or ECM software updates. The differentia
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FMI 5: Current below normal or open circuit
This fault code indicates the ECM detected an open circuit or current below the normal threshold on the secondary ASR (Automatic Slip Regulation) valve solenoid circuit. In practice, this commonly appears after a wiring harness repair near the rear axle or following a valve replacement where the con
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FMI 6: Current above normal or grounded circuit
The SPN 807 FMI 6 fault code indicates a current above normal or grounded circuit in the ASR Valve circuit, a crucial part of the Anti-Slip Regulation system. This issue often arises in vehicles after a control module replacement or when moisture infiltrates the electrical connectors. In practice, t
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FMI 7: Mechanical system not responding properly
SPN 807 FMI 7 indicates the Differential 2 Anti-Slip Regulation valve is not responding mechanically to ECM commands. This fault commonly emerges during heavy off-road operations when the valve fails to modulate differential lock engagement properly. Technicians frequently encounter this code after
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FMI 8: Abnormal frequency, pulse width or period
SPN 807 FMI 8 indicates the ECM has detected an abnormal frequency, pulse width, or period on the Differential 2 ASR (Anti-Slip Regulation) valve control circuit. This fault commonly appears after a forced DPF regeneration when the exhaust heat damages the valve wiring harness near the rear axle. Te
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FMI 9: Abnormal update rate
SPN 807 FMI 9 indicates the Differential 2 ASR valve is transmitting at an abnormal update rate on the J1939 CAN bus. The ECM expects a periodic message every 50 ms; deviation triggers this fault. Technicians often see this after a valve replacement when the harness connector is not fully seated, ca
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FMI 11: Root cause not known
SPN 807 with FMI 11 indicates a fault in the ASR Valve for Differential 2, with the root cause unknown. Technicians often encounter this code following unexpected braking behavior during adverse weather conditions when the Anti-Slip Regulation (ASR) system is heavily relied upon. In such scenarios,
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FMI 12: Bad intelligent device or component
SPN 807 FMI 12 indicates a bad intelligent device in the differential ASR (Anti-Slip Regulation) valve system. This fault commonly occurs after ECM software updates or when the valve’s internal microprocessor fails to respond to CAN communication requests. Technicians frequently encounter this code
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FMI 13: Out of calibration
SPN 807 FMI 13 indicates the differential lock Anti-Slip Regulation valve has drifted beyond acceptable calibration parameters. This fault commonly emerges after extensive off-road operations or following ECM replacement without proper valve adaptation procedures. The ASR valve requires precise pres
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FMI 14: Special instructions
SPN 807 FMI 14 is associated with the Differential 2 – ASR Valve and indicates special instructions are required. This fault often appears after routine maintenance or when an ASR system component, such as the valve, is replaced. Technicians frequently encounter this code when the ECM does not recog
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FMI 18: Data valid but below normal operating range (moderately severe)
SPN 807 FMI 18 indicates the Differential 2 Anti-Slip Regulation (ASR) valve signal is valid but operating below normal parameters. This fault commonly appears on MAN and Mercedes-Benz commercial vehicles during muddy terrain operations when the differential lock system experiences prolonged engagem
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FMI 31: Condition exists
This fault indicates the ECM has detected a continuous condition on the ASR (Automatic Slip Regulation) valve circuit for differential 2. The valve controls air pressure to the differential lock actuator. Technicians often encounter SPN 807 FMI 31 after a forced DPF regeneration where high exhaust h