Diagnostic Trouble Code 41

Primary Crash Sensor High Resistance Or Open In Circuit

Normal Description

Each primary crash sensor has an internal resistor. The diagnostic monitor uses the resistor in the primary crash sensors in combination with the two resistors inside the diagnostic monitor to create a tightly controlled diagnostic voltage at Pin 11 (Circuit 614, GY/O). The primary crash sensors are tied together inside the diagnostic monitor at Pins 17 (Circuit 617, PK/O), 18 (Circuit 619, PK/W) and 19 (Circuit 621, W/Y). Therefore, the resistors in the sensors are connected in parallel. The parallel combination of all three sensor resistors should be equal to 393 ohms. The resistance of each sensor should be 1180 ohms.

The resistors inside the diagnostic monitor are connected to Pins 11 (Circuit 614, GY/O) and 12 (Circuit 623, P/W) and are equal in value. Note that Circuits 614 and 623 are tied together inside the safing sensor. Therefore, the two resistors inside the diagnostic monitor are connected in parallel and will function the same as one resistor of half the original value. Current flows from Pins 1 and 6 through the resistors, out to Circuits 614 (GY/O) and 623 (P/W) on Pins 11 and 12, through the safing sensor and out to the driver side air bag. Current flows through the driver side air bag and into Pin 10 (Circuit 615, GY/W). Current then flows from Pin 10 through the diode inside the diagnostic monitor and out to the primary crash sensors through Pins 17, 18 and 19. The current flows through each primary crash sensor resistor and terminates at the case ground of each sensor. Pin 11 is the midpoint of the resistor network and voltage at Pin 11 will change with vehicle charging system voltage. The expected voltage at Pin 11 is shown in the table below. The diagnostic monitor measures the vehicle charging system voltage at Pin 13 (battery input). By measuring the voltage at Pin 13, the diagnostic monitor can accurately predict what the voltage at Pin 11 should be in a normal functioning system.

If the resistance of one or more of the primary crash sensors has increased in value, then the parallel equivalent resistance of the primary crash sensors will be greater than 393 ohms. When primary crash sensor resistance increases, there is less overall resistance pulling the diagnostic voltage down. Therefore, the voltage at Pin 11 will increase and the diagnostic monitor will flash Diagnostic Trouble Code 41 to indicate high resistance (or an open circuit) in one of the primary crash sensor circuits. Another situation that may cause high voltage on Pin 11 is if resistance builds up across the normally open safing sensor contacts. The safing sensor does not normally have resistance across its contacts. If resistance appears across the safing sensor contacts, then current will flow from Pin 15 (Circuit 611, W/O) through the abnormal resistance across the safing sensor contacts and into Circuit 614 (GY/O). Since the voltage at Pin 15 is battery voltage or higher, this will also cause an increase in voltage at Pin 11 and the diagnostic monitor will flash Diagnostic Trouble Code 41.

Possible Causes

Higher than normal voltage on Pin 11 can be caused by:

1. An open in one or more of the circuits between the diagnostic monitor and the primary crash sensors. Circuits 617 (PK/O), 619 (PK/W), or 621 (W/Y) may have an open circuit in the wiring.

2. An abnormally high resistance value across one or more of the primary crash sensors. One or more of the primary crash sensor resistors may have too high resistance or may be completely open circuit.

3. Resistance across the safing sensor. The safing sensor is a normally open switch with infinite resistance across its contacts. If the safing sensor is damaged and some resistance builds up across the open contacts, the voltage on Circuit 611 (W/O) will pull up the voltage on Circuit 614 (GY/O).

4. An intermittent open between the positive terminal of the battery and Pin 13 may cause the diagnostic monitor to determine that voltage on Pins 17, 18 and 19 is too high with respect to the voltage on Pin 13.
   
   

   CHARGING SYSTEM VOLTAGE

   Charging System Voltage	Voltage at PIN NO. 10	Voltage at PIN NO. 11	Voltage at PIN NO. 17	Voltage at PIN NO. 18	Voltage at PIN NO. 19
   9.0	1.9	1.9	1.4	1.4	1.4
   9.5	2.0	2.0	1.5	1.5	1.5
   10.0	2.1	2.1	1.6	1.6	1.6
   10.5	2.2	2.2	1.7	1.7	1.7
   11.0	2.3	2.3	1.8	1.8	1.8
   11.5	2.4	2.4	1.9	1.9	1.9
   12.0	2.5	2.5	2.0	2.0	2.0
   12.5	2.6	2.6	2.1	2.1	2.1
   13.0	2.7	2.7	2.2	2.2	2.2
   13.5	2.7	2.7	2.3	2.3	2.3
   14.0	2.9	2.9	2.4	2.4	2.4
   14.5	3.0	3.0	2.5	2.5	2.5
   15.0	3.1	3.1	2.6	2.6	2.6
   15.5	3.2	3.2	2.7	2.7	2.7
   16.0	3.3	3.3	2.8	2.8	2.8

   
   

DIAGNOSTIC TROUBLE CODE 41

41-1 VERIFY CONDITION

• Turn key to ON.

• Count diagnostic trouble code.

• Is code 41 flashing?

GO to 41-2.

No
Read the normal operation description for this diagnostic trouble code. EXAMINE the diagnostic trouble code schematic and look for areas where intermittent conditions would occur (connectors, splices, crimps, etc.).
DO NOT proceed with Pinpoint Test until the code is flashing!
Failure to do so will result in needless replacement of the air bag system components and repeat service.

 

41-2 CHECK FOR INTERMITTENT OPEN IN BATTERY FEED

• Deactivate system.

• Turn ignition switch from OFF to RUN.

• Measure voltage between Pin 13 (+) and Pin 3 (-). Record voltage as charging system voltage.

• Measure voltage between Pin 11 (Circuit 614 (GY/O)) and Pin 3 (ground).

  NOTE: Use voltage table to determine if voltage at Pin 11 is within specifications.

• Is voltage measured within specification (within ± 1 volt)?

Yes
TURN ignition switch to OFF. INSPECT all terminals and connections between the positive terminal of the battery and Pin 13 of the diagnostic monitor. This includes the fuse terminal crimps, splices, etc. GO to 41-3.

No
GO to 41-4.

 

41-3 SERVICE POOR CONNECTIONS

• During inspection of all terminals and connections, were any poor connections found?

Yes
SERVICE as required. RECONNECT system. VERIFY system. REACTIVATE system.

No
REPLACE diagnostic monitor. RECONNECT system. VERIFY system. REACTIVATE system.

 

41-4 CHECK PRIMARY CRASH SENSOR RESISTANCE

• Turn ignition switch OFF.

• Disconnect diagnostic monitor.

• Measure resistance of all primary crash sensor circuits from Pins 17, 18 and 19 of diagnostic monitor harness connector to Pin 3 (ground).

• All resistances should be 1180 ± 20 ohms.

• Are all measurements within specifications?
  
  
  
  
  

Yes
GO to 41-6.

No
LOCATE and DISCONNECT primary crash sensor with abnormal reading.
GO to 41-5.

 

41-5 MEASURE RESISTANCE OF ABNORMAL PRIMARY CRASH SENSOR

• Measure resistance across the two circuits in the primary crash sensor connector.

• Is reading within specification (1180 ± 20 ohms)?

Yes
LOCATE and SERVICE open circuit in wiring harness for affected sensor. RECONNECT system. VERIFY system. REACTIVATE system.

No
REPLACE affected crash sensor. RECONNECT system. VERIFY system. REACTIVATE system.

 

41-6 CHECK RESISTANCE ACROSS PINS 15 AND 11

• Place ohmmeter on highest ohm scale available (200K ohms or AUTO).

• Measure resistance across Pin 15 (Circuit 611 (W/O)) and Pin 11 of the diagnostic monitor harness connector.

• Is resistance infinite (open)?

Yes
LOCATE and SERVICE short between air bag circuits (614, 615) and B+ in the wire harness. RECONNECT system. VERIFY system. REACTIVATE system.

No
GO to 41-7.

 

41-7 CHECK SAFING SENSOR

• Disconnect LH B-pillar safing sensor.

• Measure resistance across Circuit 614 (GY/O) and Circuit 611 (W/O) wires in safing sensor connector.

• Is reading greater than 100,000 ohms?
  
  
  
  
  

Yes
LOCATE and SERVICE short between Circuit 611 and 614 in wiring harness. RECONNECT system. VERIFY system. REACTIVATE system.

No
REPLACE LH B-pillar safing sensor. RECONNECT system. VERIFY system. REACTIVATE system.

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