My '98 C5 is displaying code 1780c[ loss of steering position signal] Can someone define this for me? I would like to avoid the dealership for obvious reasons. Thanks.

 

Here is the exact description of the code form GM Service on the web. Hope it helps...

Document ID# 221164
1998 Chevrolet Corvette


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DTC C1780 Loss of Steering Position Signal




Circuit Description
The ESC module receives a steering position PWM signal from the Electronic Brake/Traction Control Module (EBTCM) on CKT 914. The ESC module uses this signal in order to determine the shock absorber control levels and will command a more firm setting if the vehicle is in a turn. The ESC module monitors the steering position circuit and can determine if a valid signal is sent from the EBTCM.

Conditions for Setting the DTC
• The ESC module does not detect a valid steering position PWM signal from the EBTCM.

• The condition must be detected for 5 seconds in 4 consecutive ignition cycles.

Action Taken When the DTC Sets
• Stores a DTC C1780 in the ESC memory.

• Ignores the steering position PWM input.

• Will continue to control the shock absorbers using the lateral acceleration data sent from the EBTCM on the serial data line.

• Sends a message to the IPC to display the SERVICE RIDE CONTROL message.

Conditions for Clearing the DTC
• The ESC module detects a valid steering position PWM signal from the EBTCM.

• A history DTC will clear after 100 consecutive ignition cycles if the condition for the malfunction is no longer present.

• The IPC clearing DTCs feature.

• Using a scan tool.

Diagnostic Aids
• The following conditions may cause an intermittent malfunction:

- An intermittent open or short (to ground or to voltage) on the steering position sensor CKT 914.

- Intermittent operation of the EBTCM. Refer to ABS Diagnostic System Check .

• If the ESC module does not receive a valid steering position PWM signal from the EBTCM, the RTD system will still function, but will ignore the steering position PWM signal. The RTD system uses lateral acceleration data sent from the EBTCM on the serial data line in order to substitute for a loss of the steering position PWM signal.

• The ESC module uses an ignition cycle counter diagnostic approach to set this DTC. This requires the ESC module to detect the malfunction 4 times before setting the DTC. To disable this feature, use a scan tool to clear all DTCs before preforming diagnostic procedures.

• An intermittent open or short (to ground or to voltage) on the steering position PWM circuit may cause a random firm/soft ride condition.

• If the DTC is a history DTC, the problem may be intermittent. Using a scan tool, monitor the steering position sensor circuit while moving the related wiring and connectors. This can often cause the malfunction to appear.

Test Description
The numbers below refer to the step numbers on the diagnostic table:

This step checks if any ABS/TCS DTCs are present. The EBTCM provides the ESC module with steering position data, therefore all ABS/TCS DTCs that are associated with the steering position sensor must be diagnosed and corrected before attempting to diagnose a DTC C1780.

This step checks if the ESC module is able to receive a steering position PWM signal from the EBTCM.

This step checks for opens or shorts (to ground or to voltage) on the steering position signal CKT 914.

This step checks for an intermittent malfunction and requests a thorough inspection of the related steering position sensor circuit wiring and connectors.

DTC C1780 -- Loss of Steering Position Signal Step
Action
Value(s)
Yes
No

1
Was the RTD Diagnostic System Check performed?
--
Go to Step 2
Go to RTD Diagnostic System Check

2
Using a scan tool, check for any stored ABS/TCS DTCs.

Are any ABS/TCS DTCs stored?
--
Go to ABS Diagnostic System Check
Go to Step 3

3
Using a scan tool, monitor the steering position PWM input while turning the steering wheel.

Does the PWM reading change when the steering wheel is turned?
--
Go to Step 5
Go to Step 4

4
Check for an open or a short (to voltage or to ground) on CKT 914.

Was a circuit problem found and repaired?
--
Go to Step 8
Go to Step 5

5
Check the steering position signal circuit for an intermittent malfunction. Refer to Diagnostic Aids.

Was an intermittent malfunction found and repaired?
--
Go to Step 8
Go to Step 6

6
Turn OFF the ignition switch.
Connect or install any connectors or components that were disconnected or removed.
Turn ON the ignition switch.
Using a scan tool, select clear DTCs.
After 5 seconds, check if DTC C1780 resets.
Does DTC C1780 reset?
--
Go to Step 7
System OK

7
Replace the ESC module. Refer to Electronic Suspension Control Module Replacement .

Is the repair complete?
--
Go to Step 8
--

8
Turn OFF the ignition switch.
Connect or install any connectors or components that were disconnected or removed.
Turn ON the ignition switch.
Using a scan tool, select clear DTCs.
Is the repair complete?
--
Go to RTD Diagnostic System Check
--



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Document ID# 221164
1998 Chevrolet Corvette

 

Not to steal the thread.
What is "GM Service on the Web"?
Can anyone access this?
Barrier

 

RichieRichZ06 seems to be able to get in. I haven't been able to access the site. You can read about it at GM Service and I sent an Email to RichieRichZ06 but haven't heard anything yet. Sounds exceptional with drawings and explanations of how to do anything on the car.

 

It is a dealership only website. It is called dealerworld and has all sorts of cool info on all cars. It is not able to be accessed by the general public, but if you have stuff you need, please let me know and I can look into it for you.

 

Hopefully you got my email. If not please let me know. Our email here at work is a POS sometimes. RICH