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kingjim9
User
Apr 25, 2009, 12:40 PM
Post #1 of 13
(2742 views)
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1995 Chevy 1500 pickup 4.3L V6, the check engine light is on, i'm going to go down to it and read the code in a minute, but also the oil pressure is reading real low at idle but when the accelerator is pressed down any little bit it goes back up to normal. Any ideas on what could be causing this?
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 25, 2009, 12:52 PM
Post #2 of 13
(2740 views)
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One may have nothing to do with the other. It's normal for oil pressure to be low at idle. It's just a question of whether it's too low or not. Get the codes read and we'll see what you have. You might want to change the oil in the meantime to see if it helps the oil pressure problem also.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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kingjim9
User
Apr 25, 2009, 2:35 PM
Post #3 of 13
(2735 views)
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how can i pull the codes on it because my OBD II code reader doesn't fit into the slot on the truck?
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 25, 2009, 2:41 PM
Post #4 of 13
(2729 views)
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Your kinda screwed with this one. This is the transition year from OBD1 to OBD2 and many of the GMs are hybrids of both systems and can only be read with a professional scan tool.
If by chance you have to old OBD1 style connecter, jump the top right 2 (A & B) terminals together and turn the key on and the check engine light will flash codes but i suspect you have an OBD2 plug but an OBD1 system.
Here is what the old system looks like
Diagnostic Trouble Codes - 1994
Chevrolet 13 Open Oxygen Sensor Circuit
14 Coolant Temperature Sensor (High Temp Indicated)
15 Coolant Temperature Sensor (Low Temp Indicated)
21 Throttle Position Sensor (Signal Voltage High)
22 Throttle Position Sensor (Signal Voltage Low)
23 Manifold Air Temperature (MAT) Low Temp Indicated
24 Vehicle Speed Sensor (VSS) Circuit
25 Manifold Air Temperature (MAT) High Temp Indicated
32 Exhaust Gas Recirculation (EGR) Circuit
33 Manifold Absolute Pressure Sensor Circuit (High Sig.)
34 Manifold Absolute Pressure Sensor Circuit (Low Sig.)
35 Idle Air Control (IAC)
41 Cylinder Select Error
42 Ignition Control (IC) Circuit
43 Knock Sensor (KS) Circuit
44 Oxygen Sensor Circuit (Lean Exhaust Indicated)
45 Oxygen Sensor Circuit (Rich Exhaust Indicated)
51 EEPROM or ECM Failure
53 System Voltage Overcharge
54 Fuel Pump Circuit (Low Voltage)
55 ECM Error 61 Degraded Oxygen Sensor
62 Transaxle Gear Switch Signal Circuit 63 A/C Refrigerant Pressure Sensor Circuit
To extract a trouble from the computer for diagnostic purposes, the Assembly Line Communication Link (ALDL) connector is used.
Ground terminals A and B with the ignition "ON" and engine not running. The system will enter the diagnostic mode. In this mode, the computer will display a 12, three consecutive times, by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" or light. A 12 consists of one flash, a short pause, then two flashes in rapid succession.
After 12 is displayed, any stored trouble s will be displayed by flashing the "CHECK ENGINE", "SERVICE ENGINE SOON" or "MALFUNCTION INDICATOR LAMP" light. All s are displayed 3 times each then a 12 will repeat. In the diagnostic mode, the computer will also energize all computer controlled relays and solenoids. 
ALDL Connector (Located Underdash)
The ALDL diagnostic connector is located in the passenger compartment.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Apr 25, 2009, 2:42 PM)
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kingjim9
User
Apr 25, 2009, 2:46 PM
Post #5 of 13
(2723 views)
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i think i have an OBD I style connecter because the OBD II doesn't even fit over it at all, what do you mean by jump the top right 2 terminals together? Do you want me to just connect them somehow with the ignition on?
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 25, 2009, 2:48 PM
Post #6 of 13
(2717 views)
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I just posted the complete instructions
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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kingjim9
User
Apr 25, 2009, 4:06 PM
Post #7 of 13
(2704 views)
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Alright i crossed those two terminals and got codes 12, 22, 34
which as you listed are:
22: TPS Low Voltage
34: Manifold Absolute Pressure Sensor Circuit (Low Sig.)
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 25, 2009, 4:09 PM
Post #8 of 13
(2698 views)
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You could have a bad TPS but it would need to be tested manually.
Check the vacuum supply to the MAP.. The sensor may be bad also..
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
(This post was edited by Hammer Time on Apr 25, 2009, 4:14 PM)
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Tom Greenleaf
Ultimate Carjunky
/ Moderator
Apr 25, 2009, 5:03 PM
Post #9 of 13
(2690 views)
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To add: TPS can be checked with a simple ohm meter. MAP = actually means manifold vacuum (MAP = Manifold Actual Pressure witch includes Vacuum) actually which at idle should be around 18 Hgs of mercury. All this could be a stupid vacuum leak,
T
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kingjim9
User
Apr 27, 2009, 9:20 AM
Post #10 of 13
(2674 views)
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I actually re-checked the codes on it today and got 13, 34, 44 and one thing i noticed up above, when you posted what all the codes ment it says for a '94 my truck is a '95, will that make any difference in the trouble codes?
13,44 are for an open o2 sensor circuit, and lean exhaust indicated respectively
and 34 is still for the MAP sensor (low sig.)
what do you guys think?
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 27, 2009, 9:30 AM
Post #11 of 13
(2669 views)
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The codes are the same. I intentionally gave you 94 because 95 is supposed to have an OBD2 connecter but like I said, it was a transition year and you never know what you will find.
I would say you need to resolve the MAP code for as it could be causing the lean code also. You would need a digital voltmeter to read the signal return voltage. It should start around half a volt at full vacuum and increase up to about 5 volts and the vacuum is reduced. It's either got an open circuit to the MAP of a bad MAP.
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We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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kingjim9
User
Apr 27, 2009, 9:49 AM
Post #12 of 13
(2665 views)
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where is the MAP sensor at on this truck?
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Hammer Time
Ultimate Carjunky
/ Moderator
Apr 27, 2009, 9:59 AM
Post #13 of 13
(2660 views)
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It's mounted to the inside of the passenger side valve cover.
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