Computer/integrating Systems: Diagnosis Saturn ION I

Scan Tool Output Controls

Scan Tool Output Controls

Scan Tool Data List

Body Control Module (BCM)

Circuit Description

The internal fault detection is handled inside the control module. No external circuits are involved.

DTC Descriptor

This diagnostic procedure supports the following DTC

DTC B1000 Electronic Control Unit (ECU) Performance

Conditions for Running the DTC

The microprocessor runs the program to detect an internal fault when power up is commanded. The only requirements are voltage and ground. This program runs even if the voltage is out of the valid operating range.

Conditions for Setting the DTC

1. The control module detects an internal write malfunction.
2. The control module detects an internal checksum malfunction.

Action Taken When the DTC Sets

The microprocessor refuses all additional inputs.

Conditions for Clearing the DTC

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

Diagnostic Aids

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1000

Some control modules must be configured with serial numbers, vehicle options, or other information. If a control module was not properly configured after installation, that module may set DTC B1001.

This diagnostic procedure supports the following DTC

DTC B1001 Option Configuration Error

The ignition is ON.

The control module is not configured properly.

1. The SERVICE VEHICLE SOON indicator illuminates.
2. The check gages chime sounds.

1. A current DTC B1001 will clear when the module is correctly programmed.
2. A history DTC B1001 will clear after the ignition has been cycled 100 times, without a repeat of the malfunction.

The most likely reasons for DTC B1001 being set are incorrect calibration files were downloaded to the module, or the module was replaced without the recalibration having been performed.

The internal fault detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1004 Electronic Control Unit Identification Circuit

The module microprocessor must be active/awake.

This DTC indicates the keep alive memory (KAM) in the module has been reset. It is a normal occurrence when battery positive voltage or ground is removed from the module, such as a battery disconnect.

The microprocessor reverts back to the base programmed critical operating data until new data is learned and stored in KAM.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1004

The electrically erasable programmable read-only memory (EEPROM) checksum error detection is handled inside the control module. No external circuits are involved.

This diagnostic procedure supports the following DTC

DTC B1009 EEPROM Checksum Mismatch

The module runs the program to detect an EEPROM checksum error after each wake-up. The only requirements are battery positive voltage and ground. This program runs even if the voltage is out of the valid operating range.

The module retains an inverse copy of the digital value stored in certain blocks of memory in the EEPROM. The module then reads the information from those certain blocks and adds the stored inverse value to the current value. If they do not equal 0, the module sets the DTC.

The module reverts to base operation values programed for those blocks of data that have failed the checksum test. The blocks of data that have not failed the checksum test are not affected.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC may be stored as a history DTC without affecting the operation of the module. If stored only as a history DTC and not retrieved as a current DTC, do not replace the module.
2. If this DTC is retrieved as both a current and history DTC, replace the module.

DTC B1009

Scheme 11

The body control module (BCM), monitors the ignition inputs Off/Run/Crank, Run/Crank and the accessory signals supplied from the ignition switch. The BCM uses the sequence that the signals appear and their voltage levels to determine the power mode called for by the vehicle operator using the ignition switch. A fuse protected B+ voltage source is supplied by the BCM to the ignition switch over a discrete circuit. The ignition switch uses this voltage for Run/Crank signal discrimination. The Run/Crank signal is also routed to the vehicles Run/Crank relay control coil.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC B1372 Device Ignition 1 (ON and START) Circuit Low
2. DTC B1373 Device Ignition 1 (ON and START) Circuit High
3. DTC B1374 Device Ignition 1 (ON and START) Circuit Open

1. The BCM must be powered and must detect a change in the ignition switch circuit states.
2. The vehicles battery must be fully charged.

Conditions for Running the DTCs

1. Voltage supplied to the module is in the normal operating voltage range.
2. The vehicle power mode requires serial data communication to occur.

The module uses default values for all parameters received on the class 2 serial data circuit.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. These DTCs cannot be retrieved with a current status. Diagnosis of current DTCs is accomplished via the symptom, Scan Tool Does Not Communicate with a Class 2 Device. Refer to «Scan Tool Does Not Communicate with Class 2 Device»(ref-196943-S15878844672005101000000) .
2. An intermittent condition is likely to be caused by a short on the class 2 serial data circuit. Use the Scan Tool Does Not Communicate with a Class 2 Device procedure in order to isolate an intermittent condition. Refer to «Scan Tool Does Not Communicate with Class 2 Device»(ref-196943-S15878844672005101000000) .

The controller area network (CAN) serial data line is a high speed serial data bus used to communicate information between the engine control module (ECM), body control module (BCM), and the transmission control module (TCM). Typical data-transmission speeds must be high enough to ensure the required real-time response is maintained. The CAN serial data line does not communicate with the scan tool via the data link connector (DLC). CAN serial data information is interpreted by the BCM and transmitted to the serial data line by the BCM.

Modules connected to the CAN serial data circuit monitors communication during normal vehicle operation, where operation information is exchanged among the modules. Each module on the CAN network maintains a transmit error counter (TEC) and a receive error counter (REC). The counter values increase with detected errors and will decrease with error-free messages. If the TEC value exceeds 255, the controller removes itself from the network and DTC U2100 will result.

This diagnostic procedure supports the following DTC

DTC U2100 Controller Area Network (CAN) Bus Communication

1. Supply voltage to the modules are in the normal operating range.
2. The vehicle is in the RUN power mode.

The module setting the DTC has attempted to establish communications on the CAN circuits for more than 7 times.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. This DTC cannot be retrieved with a current status. Diagnosis of current DTC is accomplished via the symptom, Scan Tool Does Not Communicate with High Speed GMLAN Device.
2. An intermittent condition is likely to be caused by a short on the GMLAN serial data circuits. Use the Scan Tool Does Not Communicate with High Speed GMLAN Device procedure in order to isolate an intermittent condition.

DTC U2100

The controller area network (CAN) serial data line is a high speed serial data bus used to communicate information between the engine control module (ECM), body control module (BCM), and the transmission control module (TCM). Typical data-transmission speeds must be high enough to ensure the required real-time response is maintained. The CAN serial data line does not communicate with the scan tool via the data link connector (DLC). CAN serial data information is interpreted by the BCM and transmitted to the serial data line by the BCM. The CAN bus is continuously monitored by the modules on the serial data bus.

This diagnostic procedure supports the following DTCs

1. U2103 Fewer Controllers On Bus Than Programmed
2. U2104 Controller Area Network (CAN) Bus Reset Counter Overrun

1. Supply voltage to the modules are in the normal operating range.
2. The ignition is cycled from OFF to RUN.

1. A current DTC clears when the malfunction is no longer present.
2. A history DTC clears when the module ignition cycle counter reaches the reset threshold, without a repeat of the malfunction.

1. DTC U2103 is likely an intermittent condition caused by a open on the GMLAN serial data circuits. Use the Scan Tool Does Not Communicate with High Speed GMLAN Device procedure in order to isolate an intermittent condition.
2. DTC U2104 cannot be retrieved with a current status. Diagnosis of current DTC is accomplished via the symptom, Scan Tool Does Not Communicate with High Speed GMLAN Device.

DTC U2103 or U2104

The controller area network (CAN) serial data line is a high speed serial data bus used to communicate information between the engine control module (ECM), body control module (BCM), and the transmission control module (TCM). Typical data-transmission speeds must be high enough to ensure the required real-time response is maintained. The CAN serial data line does not communicate with the scan tool via the data link connector (DLC). CAN serial data information is interpreted by the BCM and transmitted to the serial data line by the BCM.

The CAN bus is continuously monitored by the serial data bus. Each module on the CAN serial data circuit learns the identity of the other modules on the circuit. If a module stops communicating after all modules have initiated for the igniting cycle, other module set a DTC specific for the module not communicating

1. DTC U2105, can not communicate with the ECM
2. DTC U2106, can not communicate with the TCM
3. DTC U2172, can not communicate with the Radio

DTC U2105-U2199

This diagnostic procedure supports the following DTCs

1. DTC U2105 Lost Communications With Engine Control System
2. DTC U2199 Unassigned

1. Supply voltage to the modules are in the normal operating range.
2. The vehicle is in the RUN power mode.

The module setting the DTC has attempted to establish communications on the CAN circuits for more than 7 times.

Besides storing the DTC as both current and history, and using default values for missing parameters, the modules on the CAN network each take separate actions as listed

1. ECM Turn ON the malfunction indicator lamp (MIL) during the second consecutive drive cycle with the error detected. Record the operating conditions at the time of turning ON the MIL and store the data as Freeze Frame information.
2. TCM Send a request to the ECM to turn ON the MIL during the second consecutive drive cycle with the error detected.
3. BCM Turn ON the MIL during the second consecutive drive cycle with the error detected. Record the operating conditions at the time of turning ON the MIL and store the data as Freeze Frame information.

The MIL is cleared, turned OFF, and the DTC is cleared by a different strategy for each module.

1. ECM If the fault is not detected 3 consecutive drive cycles, the current DTC is cleared and the MIL is turned OFF. The history DTC is cleared if the malfunction does not reoccur for 40 consecutive drive cycles. The history DTC is cleared if there is a keep alive memory (KAM) reset (battery disconnected).
2. TCM If the fault is not detected one consecutive drive cycle, the current DTC is cleared. The history DTC is cleared if the malfunction does not reoccur for 40 consecutive drive cycles.
3. BCM If the fault is not detected 3 consecutive drive cycles, the current DTC is cleared and the MIL is turned OFF. The history DTC is cleared if the malfunction does not reoccur for 40 consecutive drive cycles. The history DTC is cleared if there is a KAM reset, battery disconnected.

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the systems. Refer to «Checking Aftermarket Accessories»(ref-196941-S26961180052005101000000) in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

1. «Scan Tool Does Not Power Up»(ref-196943-S00544728872005101000000)
2. «Scan Tool Does Not Communicate with Class 2 Device»(ref-196943-S15878844672005101000000)
3. «Scan Tool Does Not Communicate with High Speed GMLAN Device»(ref-196943-S09915820712005101000000)
4. «Retained Accessory Power (RAP) On After Timeout»(ref-196943-S21968414692005101000000)
5. «Retained Accessory Power (RAP) Inoperative»(ref-196943-S30200631962005101000000)

The data link connector (DLC) is a standardized 16 cavity connector. Connector design and location is dictated by an industry wide standard, and is required to provide the following

1. Scan tool power battery positive voltage at terminal 16
2. Scan tool power ground at terminal 4
3. Common signal ground at terminal 5

The scan tool will power up with the ignition OFF. Some modules, however, will not communicate unless the ignition is ON, and the power mode master (PMM) module sends the appropriate power mode message.

Modules connected to the class 2 serial data circuit monitor for serial data communications during normal vehicle operation. Operating information and commands are exchanged among the modules. Connecting a scan tool to the data link connector (DLC) allows communication with the modules for diagnostic purposes.

The engine will not start when there is a total loss of class 2 serial data communication while the ignition is OFF. The serial data bus can not be used to analyze a malfunction on the class 2 serial data bus. The following conditions will cause a total loss of class 2 serial data communication

1. A class 2 serial data circuit shorted to ground. A history U1300 will set in all modules. Refer to «DTC U1300, U1301, or U1305»(ref-196943-S37804204812005101000000) .
2. A class 2 serial data circuit shorted to voltage. A history U1301 will set in all modules. Refer to «DTC U1300, U1301, or U1305»(ref-196943-S37804204812005101000000) .
3. An internal condition within a module or connector on the class 2 serial data circuit, that causes a short to voltage or ground to the class 2 serial data circuit.

Scan Tool Does Not Communicate with High Speed GMLAN Device

Modules connected to the GMLAN serial data circuit monitor for serial data communications on the GMLAN network during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module detects a bus-off condition a DTC U2100 will be set. This DTC can be retrieved as history only.

The engine will not start when there is a total malfunction of the GMLAN serial data circuits while the engine is not running. The following conditions may cause a total loss of GMLAN data communication

1. Any of the serial data circuits shorted to ground.
2. Any of the serial data circuits shorted to voltage.
3. A short between serial data circuits.
4. An internal malfunction of a module on the GMLAN network that causes a short to voltage or ground.

Scan Tool Does Not Communicate with High Speed GMLAN Device

Scan Tool Does Not Communicate with Low Speed GMLAN Device

Modules connected to the GMLAN serial data circuit monitor for serial data communications on the GMLAN network during normal vehicle operation. Operating information and commands are exchanged among the modules. When a module detects a bus-off condition a DTC U2100 will be set. This DTC can be retrieved as history only.

The engine will not start when there is a total malfunction of the GMLAN serial data circuits while the engine is not running. The following conditions may cause a total loss of GMLAN data communication

1. Any of the serial data circuits shorted to ground
2. Any of the serial data circuits shorted to voltage
3. A short between serial data circuits
4. An internal malfunction of a module on the GMLAN network that causes a short to voltage or ground

Scan Tool Does Not Communicate with Low Speed GMLAN Device

Normal vehicle serial data communications and module operations will not begin until the system power mode has been identified. Discrete wires from the ignition switch contacts are monitored by a module which acts as the power mode master (PMM) in order to determine the correct power mode. The module which is the PMM communicates the system power mode to all modules on the serial data lines. Refer to Body Control System Description and Operation to identify which module is the PMM and the applicable power mode look up table.

There are 2 different communication networks on this vehicle: The class 2 network and the GMLAN network. The class 2 serial data circuit is the low speed link, and the GMLAN serial data circuit is the high speed link. Modules that need real time communications are attached to the high speed network. The engine control module (ECM) is the gateway between the networks. The purpose of the gateway is to transfer information from one network to another.

GMLAN Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the GMLAN serial data circuit. On this vehicle, only GMLAN high speed is used. That means that the serial data is transmitted on 2 wires at an average of 500 Kbps. The high speed dual wire GMLAN is a differential bus. That means that two bus lines, GMLAN high and GMLAN low are driven to opposite extremes from a rest or idle level. The idle level which is approximately 2.5 volts is considered a recessive transmitted data and is interpreted as a logic 1. Driving the lines to their extremes means adding 1 volt to GMLAN high wire and subtracting 1 volt from GMLAN low wire. This dominant state is interpreted as a logic 0. GMLAN network management supports selective start up and is based on virtual networks. A virtual network is a collection of signals started in response to a vehicle event. The starting of a virtual network signifies that a particular aspect of the vehicles functionality has been requested. A virtual network is supported by virtual devices which represents a collection of signals owned by a single physical device. So, any physical device can have one or more virtual devices. The signal supervision is the process of determining whether an expected signal is being received or not. Failsofting is the ability to substitute a signal with a default value or a default algorithm, in the absence of a valid signal. Some messages are also interpreted as a, heartbeat, of a virtual device. If such a signal is lost, the application will set a no communication code against the respective virtual device. This code is mapped on the Tech 2 screen as a code against the physical device. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.

Class 2 Circuit Description

The data link connector (DLC) allows a scan tool to communicate with the class 2 serial data line. The serial data line is the means by which the microprocessor-controlled modules that are connected to it communicate with each other. Once the scan tool is connected to the class 2 serial data line through the DLC, the scan tool can be used to monitor each module for diagnostic purposes and to check for diagnostic trouble codes (DTCs). Class 2 serial data is transmitted on a single wire at an average of 10.4 Kbps. The bus is active at 7.0 volts nominal and inactive at ground potential. When the ignition switch is in RUN, each module communicating on the class 2 serial data line sends a state of health (SOH) message every 2 seconds to ensure that the module is operating properly. When a module stops communicating on the class 2 serial data line, for example if the module loses power or ground, the SOH message it normally sends on the data line every 2 seconds disappears. Other modules on the class 2 serial data line, which expect to receive that SOH message, detect its absence; those modules in turn set an internal DTC associated with the loss of SOH of the non-communicating module. The DTC is unique to the module which is not communicating, for example, when the body control module (BCM) SOH message disappears, several modules set DTC U1064. Note that a loss of serial data DTC does not normally represent a failure of the module that set it.