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SYS warning light on 1993

 
Benjamin Benmarcellus
I love my Chevy Chevette!
Posts: 5
Joined: 02/14
Posted: 05/18/14 10:27 AM

I am getting a code 41 on my 1991.How do you get the ECM to get the fuel signal? Will replacing the PROM fix this issue?  

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wayne712222
My first time was in a Chevy
Posts: 140
Joined: 10/13
Posted: 05/18/14 12:07 PM

i am taking this is a PCM code 41...

instructions.. for a 90 i happen to have handy.

clear codes..  start engine and allow to run for one minute or until code 41 resets..

if code resets.. faulty connections to memcal.. or memcal unit not locked down.. or incorrect memcal installed..

if code does not set. code 41 is intermittent.. go to diagnostic aids section..

what kind of access did you use to get this code??? did you jump A to B .. or A to G??? at the ALDL



vetteoz who has not logged in for a few years posted..

DTC 41 is a loss or the serial data connection between the ECM and CCM
Very common on 90 - 93 cars
When this link is broken, the ECM does not get the fuel enable signal (part of VATS system ) from the CCM so it doesn't pulse the injectors
The fact the engine cranks shows the key reader and VATS component of the CCM are working correctly ; just that the ECM is not getting the right ( any ) fuel signal



what to check .. let me do some research..  be sure to check back..  

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Benjamin Benmarcellus
I love my Chevy Chevette!
Posts: 5
Joined: 02/14
Posted: 05/19/14 10:36 AM

im getting a  41 on my 1991 with the l98 replaced the ccm and cleaned the chassie grd at the battery box  and
im still getting a sys any help is appreacted thxs  

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Benjamin Benmarcellus
I love my Chevy Chevette!
Posts: 5
Joined: 02/14
Posted: 05/19/14 10:37 AM

im getting a  41 on my 1991 with the l98 replaced the ccm and cleaned the chassie grd at the battery box  and
im still getting a sys any help is appreacted thxs  

Post Reply
Benjamin Benmarcellus
I love my Chevy Chevette!
Posts: 5
Joined: 02/14
Posted: 05/19/14 10:37 AM

im getting a  41 on my 1991 with the l98 replaced the ccm and cleaned the chassie grd at the battery box  and
im still getting a sys any help is appreacted thxs  

Post Reply
wayne712222
My first time was in a Chevy
Posts: 140
Joined: 10/13
Posted: 05/19/14 06:39 PM

Circuit Description CCM DTC 41
The Serial Data Circuit is a communications link between the CCM, ECM, EBCM, and C68 HVAC programmer, if equipped. It is a master/slave configuration, with the CCM acting as master, and all the other devices communicating with each other through the CCM.
Code 41 will set if the ECM does not respond to CCM polls for more than a certain time period. Code 41 being set will also prohibit FEDS Fuel Enable from taking place (see Code 54). See: DTC 54\Central Control Module (CCM)
Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.
1. This test determines if the CCM is having a problem communicating with the ECM.
2. This test checks for an open between Serial Data 1 of the CCM and ECM serial data line 1. 3. This test checks for an open between Serial Data 2 of the CCM and ECM serial data line 1. 4. This test checks for a short to ground in CKT 800.
5. This test checks for a short to battery in CKT 800.
6. This test repeats Tests 2 through 5 using ECM serial data line 2 rather than line 1.
Diagnostic Aids
A short circuit on the serial data link will take the. whole link down. an open circuit will take down only those devices which become open-circuited.
A serial data fault may also cause an inoperative trip computer, loss of English/Metric temperature display control on the C68 Electronic HVAC control head, and loss of the "Check Gauges"function.
If this fault is present, a C68 Electronic HVAC control head LED will flash.
The ECM requires ignition power to send serial data. If the AIR BAG Fuse is blown, or the I/P-to DERM harness connector is disconnected, the ECM will not receive power and this code may set.
Check for an ECM Code 51, which will cause this code to set. The ECM Code 51 problem will also be evidenced by the inability to flash ECM codes or to read ECM codes through the CCM.


CCM DTC54

Circuit Description
The FEDS Fuel Enable System uses the serial data communication link between the CCM and the ECM to perform a password exchange routine when the ignition is turned "ON." If the password exchange routine is successfully completed, the ECM can pulse the fuel injectors "ON."
If the FEDS Fuel Enable routine is not successfully completed within 2 seconds, Code 54 will set and both the "SECURITY" and "SYS" indicators will flash together.
Test Description
Number(s) below refer to circled number(s) on the diagnostic chart.
1. Checks for ECM operation. If the "Service Engine Soon" lamp is not "ON," the ECM may not be available for FEDS exchange for one of many reasons. Perform the "Diagnostic Circuit Check" in Computers and Control Systems determine if there is a problem with the ECM.
2. Checks for an ECM Code 51. If ECM Code 51 is set, the ECM and/or MEM-CAL may have a problem which could prohibit successful FEDS exchange. Repair the ECM Code 51 condition using the ECM Code 51 chart in Computers and Control Systems before continuing. See: Powertrain Management\Computers and Control Systems\Testing and Inspection
3. Checks for CCM Code(s) 51, 52 or 53. These codes define a problem with the PASS-Key(R) itself or the PASS-Key(R) detection circuitry. If the PASS-Key(R) is not correct, the FEDS exchange will not take place.
4. Checks for a CCM Code 54 reset after most items that could affect FEDS Fuel Enable have checked out as OK. If Code 54 resets, replace the CCM.

Diagnostic Aids

It is very important that a thorough inspection of the wiring and connectors be performed. Failure to carefully and fully inspect wiring and connectors may result in misdiagnosis, causing part replacement with reappearance of the fault.
If a Serial Data Link fault occurs while the vehicle is running, FEDS will keep ECM fuel enabled to prevent a no-start condition on the next start attempt. The "SECURITY" and "SYS" indicators will flash to indicate a CCM problem has been noted and that the problem affects vehicle security. If the Serial Data Link fault occurs with the vehicle at rest and the engine not running, FEDS will not enable fuel.
If the vehicle exhibits a cranks but won't run condition, the FEDS exchange is not successfully completed. If the vehicle will not crank, the CCM is not satisfied with the PASS-Key(R) and is not allowing cranking, or there is a problem in the cranking system itself.  

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wayne712222
My first time was in a Chevy
Posts: 140
Joined: 10/13
Posted: 05/19/14 06:55 PM

please.. if you are going to work on this circuit. do not probe it with a conventional test light.. use a logic probe..

http://www.harborfreight.com/computer-safe-automotive-logic-probe-98709.html


also..

PCM Code 41 will set if the engine is running or cranking and the ECM detects voltage greater than 4.6
volts on circuit 423 (EST circuit.)

NOTE: If PCM Code 41 is set, the ECM will disable the fuel injectors to prevent flooding.

ABS Code 41, RF Solenoid Valve Fault

Ride control Code 41, 42 & 43, Selective Ride Control Switch Circuit Fault

airbag Code 41 And/or Code 42, Deployment Loop Energy Reserve Voltage Failure  

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