GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 1998 🢒 Seville 🢒 DTC 🢒 DTC C1738 Exhaust Solenoid Valve Short to GND

Circuit Description
Object Number: 305452 Size: LF

The ALC exhaust solenoid valve is controlled (switched ON or OFF) by the CVRSS module. The control module provides a low-side drive (switched to ground) whenever exhaust activity is required and during a head-relief sequence which occurs before each compressor start-up. This drive output from the CVRSS module is continually monitored to determine if the voltage level agrees with the commanded state.

Conditions for Setting the DTC

The DTC will set when the CVRSS module measures a feedback voltage condition at pin C14 less than a preset threshold during an exhaust solenoid valve OFF-state.

The DTC will turn history when the CVRSS module no longer senses a low voltage condition at pin C14 when the exhaust solenoid valve is in an OFF-state.

Action Taken When the DTC Sets
    • ALL rear leveling activity for the remainder of the ignition cycle will be disabled.
    • The SERVICE RIDE CONTROL message will be displayed.

Conditions for Clearing the MIL/DTC
    • Use the scan tool.
    • Use the On-Board diagnostic CLEAR RSS CODES feature.

Diagnostic Aids

A temporary compressor overload (i.e., high head pressure during a cold start) may cause the Electronic Suspension Control Maxi circuit breaker to trip. This is one possible cause of DTC C1738.

A DTC C1738 fault condition is detectable only when the exhaust solenoid valve output is commanded to the OFF-state, which occurs whenever exhaust activity is not required. The CVRSS module expects to see a high voltage condition during the OFF-state.

Only electrical problems with the exhaust solenoid valve are flagged. Pneumatic blockage problems do not set a DTC, but the CVRSS module shuts off the exhaust function if no progress is made, or if excessive run time occurs. Recovery is not attempted until the ignition is cycled OFF and ON.

Check for disconnected or damaged air lines. Replace or reconnect the air lines as needed.

Test Description

Important: 

   • Do not backprobe the sensors, actuators, or any sealed connectors.
   • When all the diagnostics and repairs are complete, clear the DTCs and verify the operation.

The number(s) below refer to the step number(s) on the diagnostic table.

  1. This step checks for an open (blown) fuse.

    2.

  2. This step checks for an open (blown) fuse.

    3.

  3. This step checks for an internal short circuit condition in the exhaust solenoid valve.

    4.

  4. This step checks for a short circuit to ground condition in circuits 1342 and 322.

    5.

  5. This step checks for a short circuit to ground condition in the compressor assembly pigtail or internally to the compressor assembly.

    6.

  6. This step checks for an open circuit condition in circuit 320.

    7.

  7. This step checks for a short circuit to ground condition in circuit 320.

    8.

  8. This step checks for an open circuit condition in circuit 1342.

Step

Action

Value(s)

Yes

No

1

Was the Road Sensing Suspension Diagnostic System Check performed?

--

Go to Step 2

Go to Road Sensing Suspension Diagnostic System Check

2
  1. Turn the ignition OFF.
  2. Check for an blown ELC fuse.

Is the ELC fuse blown?

--

Go to Step 3

Go to Step 9

3
  1. Replace the ELC fuse.
  2. Turn the ignition ON with the engine off.
  3. Check to see if the ELC fuse has blown.

Is the ELC fuse blown?

--

Go to Step 4

Go to Step 6

4
  1. Turn the ignition OFF.
  2. Remove the blown fuse.
  3. Disconnect the ALC compressor assembly connector.
  4. Measure the voltage between pin C of the ALC compressor assembly connector (harness side) and ground with a J 39200 DMM.

Is the resistance the specified value?

OL

Go to Step 15

Go to Step 5

5
  1. Disconnect Rear Junction Block connector C3.
  2. Measure the resistance between ALC compressor connector terminal C (harness side) and ground with a DMM.

Is the resistance the specified value?

OL

Go to Step 16

Go to Step 14

6
  1. Turn the ignition OFF.
  2. Install a scan tool.
  3. Turn the ignition ON with the engine off.
  4. Using the "ELC Special Functions", command the ALC compressor ON.
  5. Check for a blown ELC fuse.

Is the ELC fuse blown?

--

Go to Step 7

Go to Road Sensing Suspension Diagnostic System Check

7
  1. Turn the ignition OFF.
  2. Disconnect the ALC compressor assembly connector.
  3. Measure the resistance between ALC compressor connector terminal B (harness side) and ground with a DMM.

Is the resistance the value specified?

OL

Go to Step 15

Go to Step 8

8
  1. Disconnect the Rear Junction Block connector C3.
  2. Measure the resistance between ALC compressor connector terminal B (harness side)and ground with a DMM.

Is the resistance the value specified?

OL

Go to Step 16

Go to Step 17

9
  1. Disconnect the CVRSS module connector C1.
  2. Turn the ignition ON.
  3. Measure the voltage from CVRSS module connector C1, terminal C14 (harness side), to ground with a DMM.

Is the voltage above the specified value?

10 V

Go to Step 21

Go to Step 10

10
  1. Disconnect the ALC compressor assembly connector.
  2. Measure the voltage from ALC compressor connector terminal C (harness side) to ground with a DMM.

Is the voltage above the specified value?

10 V

Go to Step 11

Go to Step 13

11

Measure the resistance between CVRSS module connector C1, terminal C14 (harness side), and the ALC compressor connector terminal A.

Is the resistance equal to or less than the value specified?

5 ohms

Go to Step 12

Go to Step 18

12

Measure the resistance between CVRSS module connector C1, terminal C14 (harness side), and ground.

Is the resistance equal to or less than the value specified?

OL

Go to Step 15

Go to Step 19

13
  1. Turn the ignition OFF.
  2. Disconnect the Rear Junction Block connector C3.
  3. Measure the resistance between Rear Junction Block connector C3, terminal B10 (harness side) and ALC compressor connector terminal C with a DMM.

Is the resistance equal to or less than the specified value?

5 ohms

Go to Step 16

Go to Step 20

14

Repair the short circuit to ground condition in CKT 1342.

Is the repair complete?

--

Go to Road Sensing Suspension Diagnostic System Check

--

15
  1. Replace the ALC compressor assembly.
  2. Replace the ALC air tubes.

Are the replacements complete?

--

Go to Road Sensing Suspension Diagnostic System Check

--

16

Replace the Rear Junction Block.

Is the repair complete?

--

Go to Road Sensing Suspension Diagnostic System Check

--

17

Repair the short circuit condition in CKT 322.

Is the repair complete?

--

Go to Road Sensing Suspension Diagnostic System Check

--

18

Repair the open circuit condition or poor connection condition in circuit 320.

Is the repair complete?

--

Go to Road Sensing Suspension Diagnostic System Check

--

19

Repair the short circuit to ground condition in CKT 320.

Is the repair complete?

--

Go to Road Sensing Suspension Diagnostic System Check

--

20

Repair the open circuit condition or poor connection condition in circuit 1342.

Is the repair complete?

--

Go to Road Sensing Suspension Diagnostic System Check

--

21
  1. Check all connections on circuits 320 and 1342 for debris, corrosion, and/or intermittent open circuit conditions. Refer to Intermittents and Poor Connections .
  2. Check circuit 320 for an intermittent short circuit to ground condition. Refer to Intermittents and Poor Connections .
  3. Install all of the connectors and components that were removed.
  4. Clear RSS DTCs. Refer to Clearing DTCs .
  5. Wait 60 seconds.
  6. Check RSS DTCs. Refer to Displaying Diagnostic Trouble Codes (DTC) .

Is DTC C1738 set?

--

Go to Step 22

Go to Road Sensing Suspension Diagnostic System Check

22
  1. Turn the ignition OFF.
  2. Replace CVRSS control module. Refer to Electronic Suspension Control Module Replacement .
  3. Install all of the connectors and components that were removed.
  4. Install the scan tool.
  5. Turn the Ignition ON with the engine off.

    6. Important: The controller must be calibrated.

  6. Calibrate the CVRSS service controller using the scan tool. Refer to Electronic Suspension Control Module Calibration .

Is the CVRSS control module calibrated?

--

Go to Road Sensing Suspension Diagnostic System Check

--