timmer1

iTrader: (1)

Hey guys, I'm having a problem with a p0405 code. I believe its called circuit a low voltage. I've checked all the wires and they seem to have the correct voltage, with exception of one. The red wire on the end of the plug has 12 volts when it isn't plugged in, and when I plug it in, it has nothing. I'm thinking this is where my problem is, but still unsure. I changed it to an egr valve that I know is operational, and came up with the same thing. Just to see if that is normal, I compared with my mom's blazer. Appears to be the same setup, but her red wire has 12 volt whether plugged in or not. Also was wondering what the downfall would be of having allen delete the egr. I'm in NY, so I have to pass emissions inspection, but I've heard of people deleting their rear o2 sensors, and still passing. Any help would be greatly appreciated. Thanks.

Truckshop

iTrader: (17)

try to light a test light or some other kind of bulb to load the circuit. if it doesn't light the the bulb then you need to find out where the wire is bad at. if the wire has a bad connection or is broken somewhere then the meter will read 12v but when you put a load on it(or plug the valve in) the bad wire will not allow the current to pass.

timmer1

iTrader: (1)

If there is a break in the wire, how would 12 volts pass thru the break? I'll try it, but seems to me, if the wire is broke then I wouldn't get anything at all.

I also metered all the wires plugged, unplugged, running, and not running.

Red was 0.032 plugged, 12 unplugged not running.
Red was -0.001 plugged, 14.14 unplugged running.

gray was 5.03 plugged or unplugged not running.
gray was 5 plugged or unplugged running.

brown was 0.703 plugged, 0.030 unplugged not running.
brown was 0.670 plugged, -0.003 unplugged running.

purple was 0.032 plugged, 0.031 unplugged not running.
purple was 0.001 plugged, -0.003 unplugged running.

white was 0.032 plugged, 0.031 unplugged not running.
white was 0.001 plugged, -0.003 unplugged running.

I was hoping someone would know what the volts are supposed to be when working properly. If I can't figure this out, I might just have to have allen delete the egr, if it will pass nys inspection. Thanks for your help.

00ChevyScott

iTrader: (10)

get a custom tune and have EGR disabled

timmer1

iTrader: (1)

I do have a custom tune with nelson performance, but will I pass inspection in NY?

Are there any downfalls to deleting the egr?

gmcdealertech

Document ID# 546847
2000 GMC Truck GMC C Sierra - 2WD


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DTC P0405 Exhaust Gas Recirculation (EGR) Position Sensor Circuit Low Voltage




Circuit Description
An exhaust gas recirculation (EGR) system is used in order to lower oxides of nitrogen (NOx) emission levels. The EGR system accomplishes this by recirculating small amounts of exhaust gas back into the combustion chamber. High combustion temperatures cause NOx. Combustion temperatures are reduced when the air and fuel mixture is diluted with the exhaust gases.

The EGR valve is designed to accurately supply exhaust gases to the engine without the use of intake manifold vacuum. The EGR valve controls the exhaust flow into the intake manifold from the exhaust manifold through an orifice with a powertrain control module (PCM) controlled pintle. The PCM controls the pintle position using inputs from the throttle position (TP) sensor, the manifold absolute pressure (MAP) sensor and, the engine coolant temperature (ECT) sensor. The PCM commands the EGR valve in order to supply the correct amount of exhaust gas recirculation for the current engine operating conditions. This can be monitored on a scan tool as the desired EGR position.

The PCM monitors the position of the EGR valve through a feedback signal. The PCM supplies a 5 volt reference circuit and a ground circuit to the EGR valve. A voltage signal representing the EGR valve pintle position is sent to the PCM from the EGR valve. This feedback signal can also be monitored on a scan tool and is the actual position of the EGR pintle. The actual EGR position should be near the desired EGR position.


Due to the moisture associated with exhaust systems, the EGR valve may freeze and stick in colder weather. After the vehicle is brought into a warm shop for repairs, the valve warms and the problem disappears. By watching the actual EGR position and the desired EGR position on a cold engine with a scan tool, the fault can be verified easily. View the Freeze Frame data to determine if the DTC set when the vehicle was cold by viewing the ECT.

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

If DTC P1635 sets at the same time, this indicates that the 5 volt reference circuit is either shorted to a ground or shorted to a voltage. The 5 volt reference circuit is internally connected within the PCM. The MAP sensor circuits may be causing this DTC to set. Refer to DTC P1635 for further diagnosis.

This step determines if the malfunction is present.

Using the Freeze Frame and Failure Records data may aid in locating an intermittent condition.

If the scan tool displays 5 volts, the EGR pintle position signal, the 5 volt reference circuit, and the PCM are OK. For any test that requires probing the PCM or component harness connectors, use the connector test adapter kit . Using this kit prevents any damage to the harness connector terminals.

If the scan tool displays 5 volts, the EGR pintle position signal circuit and the PCM are OK. For any test that requires probing the PCM or component harness connectors, use the J 35616 connector test adapter kit . Using this kit will prevent any damage to the harness connector terminals.

Disconnecting the PCM allows using the DMM in order to test the continuity of the circuits. This aids in locating an open or a shorted circuit.

Step
Action
Value(s)
Yes
No

1
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check?
--
Go to Step 2
Go to Powertrain On Board Diagnostic (OBD) System Check

2
Install a scan tool.
Idle the engine.
Monitor the Diagnostic Trouble Code (DTC) Information using the scan tool.
Did DTC P1635 fail this ignition cycle?
--
Go to DTC P1635 5 Volt Reference 1 Circuit
Go to Step 3

3
Monitor the EGR pintle position voltage on Engine 1 Data List on the scan tool.

Is the EGR pintle position voltage below the specified value?
0.14 V
Go to Step 5
Go to Step 4

4
Turn ON the ignition, with the engine OFF.
Review the Freeze Frame and Failure Records data for this DTC and observe the parameters.
Turn OFF the ignition for 15 seconds.
Start the engine.
Operate the vehicle within the conditions required for this diagnostic to run, and as close to the conditions recorded in the Freeze Frame and Failure Records as possible. Special operating conditions that you need to meet before the PCM will run this diagnostic, where applicable, are listed in Conditions for Running the DTC.
Select the Diagnostic Trouble Code (DTC) option, the Specific DTC option, then enter the DTC number using the scan tool.
If you cannot duplicate the DTC, the information included in the Freeze Frame and Failure Records data can help determine how many miles since the DTC set. The Fail Counter and Pass Counter can also help determine how many ignition cycles the diagnostic reported a pass or a fail. Operate the vehicle within the same Freeze Frame conditions, such as RPM, load, vehicle speed, temperature etc., that you observed. This will isolate when the DTC failed. For an intermittent condition, refer to Symptoms .
Does the scan tool indicate that this diagnostic failed this ignition?
--
Go to Step 5
Go to Diagnostic Aids

5
Disconnect the EGR valve electrical connector.
Jumper the 5 volt reference circuit and the EGR pintle signal circuit together at the EGR valve harness connector.
Observe the EGR pintle position voltage display on the scan tool.
Is the EGR pintle position voltage near the specified value?
5 V
Go to Step 11
Go to Step 6

6
Connect the test lamp between B+ and the EGR pintle position signal circuit at the EGR valve harness connector.
Observe the EGR pintle position voltage display on the scan tool.
Is the voltage near the specified value?
5 V
Go to Step 7
Go to Step 9

7
Turn OFF the ignition.
Disconnect the PCM connector C1 located on the same side as the manufacturer logo. Refer to Powertrain Control Module (PCM) Replacement .
Test the 5 volt reference circuit for the following conditions:
- An open

- A short to a ground

- A short to a voltage

If you find the 5 volt reference circuit is open or shorted, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find the 5 volt reference circuit open or shorted?
--
Go to Step 14
Go to Step 8

8
Inspect the 5 volt reference circuit for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If you find a poor connection, repair the terminal as necessary. Refer to Connector Repairs in Wiring Systems.
Did the terminal require replacement?
--
Go to Step 14
Go to Step 13

9
Turn OFF the ignition.
Disconnect the PCM connector C1 located on the same side as the manufacturers logo. Refer to Powertrain Control Module (PCM) Replacement .
Test the EGR pintle position signal circuit for the following conditions:
- An open circuit

- A short to a ground

- A short to sensor ground circuit

If you find the EGR pintle position signal circuit is open or shorted to a ground, repair the circuit as necessary. Refer to Wiring Repairs in Wiring Systems.
Did you find the EGR pintle position signal circuit open or shorted to a ground?
--
Go to Step 14
Go to Step 10

10
Inspect the EGR pintle position signal circuit for a poor connection at the PCM. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If you find a poor connection, repair the terminal as necessary. Refer to Connector Repairs in Wiring Systems.
Did the terminal require replacement?
--
Go to Step 14
Go to Step 13

11
Inspect for poor connections at the EGR valve. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
If you find a poor connection, repair the terminal as necessary. Refer to Connector Repairs in Wiring Systems.
Did you find and correct the condition?
--
Go to Step 14
Go to Step 12

12
Replace the EGR valve. Refer to Exhaust Gas Recirculation (EGR) Valve Replacement .

Is the action complete?
--
Go to Step 14
--

13
Important: The replacement PCM must be programmed.


Replace the PCM. Refer to Powertrain Control Module (PCM) Replacement .

Is the action complete?
--
Go to Step 14
--

14
Select the Diagnostic Trouble Code (DTC) option and the Clear DTC Information option using the scan tool.
Idle the engine at the normal operating temperature.
Select the Diagnostic Trouble Code (DTC) option and the Specific DTC option, then enter the DTC number using the scan tool.
Operate the vehicle within the Conditions for Running the DTC as specified in the supporting text, if applicable.
Does the scan tool indicate that this test ran and passed?
--
Go to Step 15
Go to Step 2

15
Select the Capture Info option and the Review Info option using the scan tool.

Does the scan tool display any DTCs that you have not diagnosed?
--
Go to the applicable DTC table
System OK



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Document ID# 546847
2000 GMC Truck GMC C Sierra - 2WD


Havent seen any of our trucks with EGR problems. Hope this helps

gmcdealertech

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This bulletin is being issued to revise DTCs P0404, P0405 and P1404 in the following Engine Controls sub-sections of the above-mentioned Service Manuals:

• Engine Controls - 4.3L

• Engine Controls - 4.8L, 5.3L, 6.0L

• Engine Controls - 5.0L, 5.7L

• Engine Controls - 7.4L

Please replace the current information in the Service Manuals with the following information.

The following information has been updated within SI2000. If you are using a paper version of any of these Service Manuals, please make a reference to this bulletin on the affected pages.

In order to properly test the EGR High Control circuit for voltage, THE ENGINE MUST BE RUNNING when using a scan tool to command the EGR valve ON. This procedure will apply to various steps in the DTC tables mentioned above. Refer to the example below for the correct procedure.

Turn OFF the ignition.
Disconnect the EGR valve harness connector.
Connect a test lamp between the EGR valve high control circuit at the EGR valve harness connector and a known good ground.
START THE ENGINE.
With a scan tool, command the EGR valve to 50%.
Does the test lamp illuminate when commanding the EGR valve on?