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1994 chevy pickup surges

Customer Question
surges and fails on its...
surges and fails on its nose after warm up has codes 13 38 42 33
Submitted: 10 years ago.Category: Chevy
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Answered in 29 minutes by:
7/3/2008
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 10 years ago
AMEDEE
AMEDEE, CHEVY TECHNICIAN
Category: Chevy
Satisfied Customers: 28,149
Experience: ASE certified tech ADVANCED LEVEL SPECIALIST. Wisconsin certified emissions state inspector
Verified

Hello there!

Sounds like you have a bad distributor or parts inside the distributor that are bad along with a bad o2 sensor. Both of which will cause a performance issue with your vehicle.

If you would like a break down of the codes, just let me know!

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Customer reply replied 10 years ago
yes give me the code breakdowns
Chevy Mechanic: AMEDEE, CHEVY TECHNICIAN replied 10 years ago

Code 13 is a heated o2 sensor circuit problem.

Circuit Description:
The PCM applies a bias voltage of approximately 450 millivolts (350-550 mV is normal bias voltage) between terminals "A10" and "A12". The Heated Oxygen Sensor (HO2S) varies the voltage within a range of about 1 volt if the exhaust is rich, and down to about .010 volt if exhaust is lean. DTC 13 is set when the voltage does not vary on CKT 412 within a predetermined amount of time.
The sensor is like an open circuit and produces no voltage when it is below 315°C (600°F). An open sensor circuit, or a cold sensor causes "Open Loop" operation.

DTC 13 Will Set When:

 

Engine has been running longer than 2 minutes.
Engine Coolant Temperature (ECT) greater than 70°C (158°F).
Throttle Position (TP) signal has been above 5%.
HO2S signal voltage steady between .35 and .55 volt.
All conditions must be met for about 60 seconds.
Action Taken (PCM will default to): The Malfunction Indicator Lamp (MIL) will illuminate and system will go into "Open Loop."

DTC 13 Will Clear When: Conditions for fault are no longer present and Tech 1 "clear DTCs" function is used or 50 ignition switch keycycles have passed with no further faults or ignition switch is turned "OFF" and ECM B fuse is removed for 10 seconds.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

 

This test verifies operating temperature and "Closed Loop" conditions.
This test checks the oxygen sensor's heating element. The heating element resistance should be 3.5 ohms at 20°C (68°F) or 14 ohms at 350°C (662°F).
This will determine if the sensor is at fault.
For this test use J 39300. This test checks the continuity of CKT 412 and CKT 413. If CKT 413 is open, the voltage on CKT 412 will be over .6 volt (600 mV).
If the fuse was open, check the wiring diagram for complete wiring circuit.
Diagnostic Aids: If the oxygen sensor heaters are not operating properly, system may go into "Open Loop" after extended idle.

Normal Tech 1 scan tool voltage varies between 100 mV to 1000 mV (.1 and 1.0 volt), while in "Closed Loop." DTC 13 sets in one minute if voltage remains between .35 and .55 volt, however the system will go "Open Loop" in about 15 seconds.

Refer to DIAGNOSIS BY SYMPTOMS/ INTERMITTENTS See: Symptom Related Diagnostic Procedures\Intermittent Condition.

An oxygen supply inside the HO2S is necessary for proper HO2S operation. This supply of oxygen is supplied through the HO2S wires. All H02S wires and connections should be inspected for breaks or contamination that could prevent reference signal from reaching the HO2S.

 

Code 38 is a brake switch circuit malfunction (except for maybe the tcc). This will have no effect on the running.

CIRCUIT DESCRIPTION
The normally closed brake switch supplies a B+ signal on CKT 420 to the PCM. The signal voltage is opened when the brakes are applied.

DTC 38 WILL SET WHEN


CKT 420 has constant voltage.
Vehicle speed is greater than 20 mph for greater than 6 seconds.
Then vehicle speed is between 5 mph and 20 mph for greater than 6 seconds.
For a complete total of seven times.
ACTION TAKEN (PCM WILL DEFAULT TO)


No Torque Converter Clutch (TCC) .
No fourth gear in hot mode.
DTC 38 WILL CLEAR WHEN
Fault condition no longer exists.

DTC CHART TEST DESCRIPTION
Number(s) below refer to circled number(s) on the diagnostic chart.


This test checks for voltage at the brake switch.
This test checks the brake switch
This test checks CKT 420 at the PCM.
DIAGNOSTIC AIDS

Code 42 is an ignition control error.

Circuit Description:
When the system is running on the ignition module, that is, no voltage on the bypass line, the ignition module grounds the IC signal. The PCM expects to see no voltage on the IC line during this condition. If it sees a voltage, it sets DTC 42 and will not go into the IC mode.

When the RPM for IC is reached (about 450 RPM), and bypass voltage is applied, the IC should no longer be grounded in the ignition module so the IC voltage should be varying.

DTC 42 Will Set When: If the bypass line is open or grounded, the ignition module will not switch to IC mode so the IC voltage will be low and DTC 42 will be set.
If the IC line is grounded, the ignition module will switch to IC, but because the line is grounded there will be no IC signal. A DTC 42 will be set.

Action Taken (PCM will default to): The PCM turns "ON" the Malfunction Indicator Lamp (MIL). (Possible ignition bypass mode depending on fault.)

DTC 42 Will Clear When: Conditions for fault are no longer present and Tech 1 "clear DTCs" function is used or 50 ignition switch keycycles have passed with no further faults or ignition switch is turned "OFF" and ECM B fuse is removed for 10 seconds.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

 

This test confirms DTC 42 and that the fault causing the DTC is present.
Checks for a normal IC ground path through the ignition module. An IC CKT 423 shorted to ground will also read less than 500 ohms; however, this will be checked later.
As the test light voltage touches CKT 424, the module should switch causing the ohmmeter to "overrange" if the meter is in the 100-200 ohm position. Selecting the 10-20,000 ohms position will indicate above 5000 ohms. The important thing is that the module "switched."
The module did not switch and this step checks for:
IC CKT 423 shorted to ground.
Bypass CKT 424 open.
Faulty ignition module connection or module.
Confirms that DTC 42 is a faulty PCM and not an intermittent in CKT 423 or 424.
Diagnostic Aids: The Tech 1 does not have any ability to help diagnose a DTC 42 problem.

 

Code 33 is a map sensor code.

Circuit Description:
The Manifold Absolute Pressure (MAP) sensor responds to changes in manifold pressure (vacuum). The PCM receives this information as a signal voltage that will vary from about 1-1.5 volts at closed throttle (idle) to 4-4.6 volts at Wide Open Throttle (WOT) (low vacuum).

DTC 33 Will Set When:

 

RPM greater than 600.
MAP signal voltage is too high (vacuum less than 96.7 kPa).
Throttle closed.
These conditions exist longer than 2 seconds.
Engine misfire or a low unstable idle may set DTC 33.
Action Taken (PCM will default to): If the MAP sensor fails, the PCM will substitute a MAP value and use the Throttle Position (TP) sensor and RPM to control fuel delivery and the malfunction indicator lamp will illuminate.

DTC 33 Will Clear When: Conditions for fault are no longer present and Tech 1 "clear DTCs" function is used or 50 ignition switch keycycles have passed with no further faults or ignition switch is turned "OFF" and ECM B fuse is removed for 10 seconds.

DTC Chart Test Description: Number(s) below refer to circled number(s) on the diagnostic chart.

 

This step will determine if DTC 33 is the result of a hard failure or an intermittent condition.
This step simulates conditions for a DTC 34. If the PCM recognizes the change, the PCM and CKT 474 and CKT 432 are OK.
Diagnostic Aids: With the ignition "ON" and the engine stopped, the manifold pressure is equal to atmospheric pressure and the signal voltage will be high. This information is used by the PCM as an indication of vehicle altitude. Comparison of this reading with a known good vehicle with the same sensor is a good way to check accuracy of a "suspect" sensor. Readings should be the same +/- .4 volt.

A DTC 33 will result if CKT 455 is open or if CKT 432 is shorted to voltage or to CKT 474.

If DTC 33 is intermittent, refer to DIAGNOSIS BY SYMPTOM/ INTERMITTENTS See: Symptom Related Diagnostic Procedures\Intermittent Condition.

 

Check all connections.
Disconnect sensor from bracket and twist sensor connections. Output changes greater than .1 volt indicates a bad connector or connection. If OK, replace sensor.
NOTICE: Make sure electrical connector remains securely fastened.

 

 

 

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