Question about 1990 Chevrolet Corvette

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I just read the diagnostic codes on my 1990 corvette. I have two codes showing on the digital speedometer A Module 1 (CCM) Code C12 A Module 4 (ECM) Code H34 What do they mean? Thanks for your help!

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Code 34 has to do with your MAP sensor I believe from what I am reading. I don't know a lot about corvettes but it says MAP sensor voltage low. The C12 code I see is a normal code set dealing with no reference pulses being received by control module. In other words with the engine not running. It has to do with No RPM reference pulse.

Posted on Sep 09, 2009

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Which terminals on obd do you short to get dtc,if you don't have scanner


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Can you tell me the location of code reader 1991 capri ?


1991 is pre-OBD2. code readers will not work.
sorry.
however, all is not lost. Many cars have an alternate way of reading codes from the computer.
Toyota has a block under the hood and you short couple wires together and count engine light flashes
Chrysler you can turn the ignition key on and off a few times and count engine light flashes
in your case for GMs from 1982 to 1995
1: find the 12 pin connector under the dash and short the upper two rightmost terminals.
with the ignition "ON" and engine not running. The system will enter the diagnostic mode. In this mode, the computer will display a Code 12, three consecutive times, by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" or light. A Code 12 consists of one flash, a short pause, then two flashes in rapid succession.
2:. After Code 12 is displayed, any stored trouble codes will be displayed by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" light. All codes are displayed 3 times each then a code 12 will repeat. In the diagnostic mode, the computer will also energize all computer controlled relays and solenoids.

Tech -- GM 2 Digit codes for 82 and up (non OBD-II)
code - code definition
12- diagnostic mode
13- 02 sensor or circuit
14- coolant sensor or circuit/ high temp indicated
15- coolant sensor or circuit/ low temp indicated
16- system voltage out of range
19- crankshaft position sensor or circuit
21- throttle position sensor or circuit- voltage high
22- throttle position sensor or circuit- voltage low
23- mixture control (m/c) solenoid or circuit (carbureted models)
23- manifold air temperature (mat) sensor or circuit (1990 and earlier models)
23- intake air temperature (iat) sensor circuit (fuel-injected models)
24- vehicle speed sensor (vss) or circuit
25- manifold air temperature (mat) sensor or circuit - high temperature indicated (1990 and earlier models)
25- intake air temperature (iat) sensor or circuit - high temperature indicated (1991 and later models)
26- quad driver module circuit
27- quad driver module circuit
28- quad driver module circuit
29- quad driver module circuit
31- park/neutral position (pnp) switch circuit
32- baro sensor or circuit (carbureted models)
32- egr circuit (fuel-injected models)
33- manifold absolute pressure (map sensor signal voltage high
33- mass air flow (maf) sensor or circuit - excessive airflow indicated
34- manifold absolute pressure (map) sensor signal voltage low 34- mass air flow (maf) sensor signal - low airflow indicated
35- idle speed control (isc) switch or circuit (shorted) (carbureted models)
35- idle air control (iac) valve/ circuit
38- brake switch circuit
39- torque converter clutch (tcc) circuit
41- no distributor signals to ecm, or faulty ignition module ( carbed models)
41- cylinders select error- mem-cal or ecm problem ( fuel-injected models
41- cam sensor circuit (3.8 engine)
42- bypass or electronic spark timing (est) circuit
43- low voltage at ecm terminal l (carbureted models)
43- knock sensor circuit
44- oxygen sensor or circuit - lean exhaust detected
45- oxygen sensor or circuit - rich exhaust detected
46- power steering pressure switch circuit
48- misfire diagnosis
51- prom, mem-cal or ecm problem
52- calpak or ecm problem
53- egr fault (carbureted models only)
53- system over-voltage (ecm over 17.7 volts)
54- mixture control (m/c) solenoid or circuit (carbureted models)
54- fuel pump circuit (1986 and later models)
55- oxygen sensor circuit or ecm
55- fuel lean monitor (2.2l engine)
61- oxygen sensor signal faulty (possible contaminated sensor)
62- transaxle gear switch signal circuits
63- manifold absolute pressure (map) sensor voltage high (low vacuum detected)
64- manifold absolute pressure (map) sensor voltage low (high vacuum detected)
66- pressure sensor or circuit air conditioning

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1 Answer

1994 legend speedometer works once in a while


92 or 94?
is fuse 22 loose?
did the CEL lamp in dash glow at this FAILURE event
or S, D or D4 auto tranny lamps flash? BINGO,

did you look for ECU/PCM errors first.? that be first .
is the odometer dead? too, at same time?
on this car the VSS module (veh.speed sensor)
sends the speed data to 6 other modules. the speedometer is 1.
so of the other 5 are dead, its the VSS dead, if not its a bad speedometer.
on of those modules is the PCM, that runs the EFI engine.
so scan it, on this old car, you insert the diagnostic jumper
(service check conn.)
and read the flash codes from the CEL lamp in the dash.
this will show 17 error, VSS bad. if bad (its bad or bad conn)
easy huh?

log in to alldata.com and read the how to read OBD1 codes
it will be something like this. (photos missing)
When a fault is noted, the ECU (otherwise known as the ECM) stores an identifying code and illuminates the CHECK ENGINE light. The code will remain in memory until cleared; the dashboard warning lamp may not illuminate during the next ignition cycle if the fault is no longer present. Not all faults noted by the ECU will trigger the dashboard warning lamp although the fault code will be set in memory. For this reason, troubleshooting should be based on the presence of stored codes, not the illumination of the warning lamp while the car is operating.
All models are equipped with a service connector in side the cabin of the vehicle. If the service connector is jumped, the CHECK ENGINE lamp will display the stored codes in the same fashion.
The 2-pin service connector is located under the extreme right dashboard on Integra, Legend & 2.5TL; on Vigor models, it is found behind the right side of the center console well under the dashboard.
Codes 1-9 are indicated by a series of short flashes; two-digit codes use a number of long flashes for the first digit followed by the appropriate number of short flashes. For example, Code 43 would be indicated by 4 long flashes followed by 3 short flashes. Codes are separated by a longer pause between transaxles. The position of the codes during output can be helpful in diagnostic work. Multiple codes transmitted in isolated order indicate unique occurrences; a display of showing 1-1-1-pause-9-9-9 indicates two problems or problems occurring at different times. An alternating display, such as 1-9-1-9-1, indicates simultaneous occurrences of the faults.
When counting flashes to determine codes, a code not valid for the vehicle may be found. In this case, first recount the flashes to confirm an accurate count. If necessary, turn the ignition switch OFF, then recycle the system and begin the count again. If the Code is not valid for the vehicle, the ECU must be replaced.
and this warning
On vehicles with automatic transaxles, the S, D or D4 lamp may flash with the CHECK ENGINE lamp if certain codes are stored. For Legend this may occur with Codes 6, 7 or 17. On Vigor and Integra it may occur with codes 6, 7 or 13. In addition, the TCS lamp on NSX may flash with codes 3, 5, 6,13,15,16,17, 35 or 36. In all cases, proceed with the diagnosis based on the engine code shown. After repairs, recheck the lamp. If the additional warning lamp is still lit, proceed with diagnosis for that system.

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1 Answer

1989 corvette camshaft sensor


Your 89 Corvette has a MEMCAL inserted in the Computer (ECM). Since the ECM used in your corvette is also found in several other GM cars the MEMCAL has the Program SPecific for that body style.

On the MEMCAL for the 89 there wis 3 Integrated Circuits (ICs) 2 are used when the car goes into Limp Home Mode. the 3rd is a EPROM (Erasible/Programable Read Only Memory). so basically to change the program you would need to use UV light and re-program the code into the EPROM.

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Nissan Consult 3 III software Professional Diagnostic Tool

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05 HYUNDAI XG MISSFIRE ON 1/3/5 CYLS AFT TIMMING BELT WAS INSALLED AND NEW PLUGS AND WIRES. RAN GOOD THE 1ST DAY AND ON THE 2 DAY STARTED THE MISS FIRE


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1990 buick lasabre with a 3.8 engine, cranks but no spark. No voltage to the primary side of coil. Code shows 22. Changed the trottle position sensor, crank position sensor and cam position sensor. Had the...


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Symptoms:
  • When flashing the Check Engine Light to read codes, code 12 will always display first, indicating the diagnostic system is active
  • The engine will not run with a "hard" code 12 set
Common Problems:
  • Chances are you will never need to diagnose a code 12. Rather, the problem would be a crank, no-start condition.
  • If code 12 does not flash, that would indicate a communication problem with the ECM.
  • Code 12 does not show when reading codes with a scan tool. If there is a communication problem, the scan tool will let you know.



OBD Code 46 - Pass-Key II System Error - Circuit out of Frequency Range The ECM receives a signal from the Pass-Key module. When the correct signal is received, the ECM will allow the engine to start and run. Please review the RepairPal article on the GM Pass-Key Anti-theft systems for more information.

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Common Problems:
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Symptoms:
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Common Problems:
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OBD Code 55 - End Test.


Hope ehit help (remember comment and rated this).

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1 Answer

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CODE 13
Trouble Code 13 indicates that the exhaust stream oxygen content sensor (O2 sensor) is not responding as expected. When cold, the sensor is 'biased' by the ECM to about 450 millivolts. Before it warms to at least 600 deg F (315 deg C) it acts as an open circuit and when the ECM reads it, it reads the 450 mV bias. The ECM expects the sensor to warm in a short period of time and begin sending its own voltages.
http://www.basinger.us/Impreza/04.%20TRANSMISSION/03.%20AUTOMATIC%20TRANSMISSION%20(DIAGNOSTICS)/11.%20List%20of%20Diagnostic%20Trouble%20Code%20(DTC).pdf
The link above is for code 74-77.

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