How the DSP5 Switch Works Grounding Issues Battery MUST Be

Having troubles with your DSP5 switch after installation?
A few simple tests using some basic tools are all that is needed to get your switch operational.
Simply start at step 1 and follow the troubleshooting steps. Do not skip any steps along the way, just
follow the guide exactly as described.
If at any point a repair is made, that does not fix the problem, return to step 1 and restart the
troubleshooting procedure to isolate any additional issues.
Before we get started at troubleshooting step 1, let’s cover some items that are important and may
impact your ability to successfully troubleshoot your switch.
How the DSP5 Switch Works
The switch is simply a resistor. It receives a 5 volt signal and ground reference from the ECM. Each
position on the switch has a different level of resistance and as the resistance in the switch changes
the voltage the ECM sees also changes.
The changing voltage is what selects the different power levels from the DSP5 tune file.
Grounding Issues
If, at some point, there is a grounding issue with the switch/ECM, the ground wire from the switch
can also be secured to a good body, chassis, or battery ground.
Battery MUST Be Fully Charged
Before beginning, ensure that your battery voltage is good (12.6v is fully charged). The ignition key
needs to be turned to the run position any time data logging is being done, and when voltage is being
checked.
Tabbed Washer Problems
During installation it is possible for the tabbed washer under the DSP5 switch knob to fall out or jump
a position or two. If this happens you will find that your switch will have more or less than 5 positions.
If your switch does not have exactly 5 positions you can correct it by removing the knob, removing
the nut, removing the lock washer, then removing the tabbed washer. Rotate the switch fully
counter-clockwise and then insert the tab on the washer between the numbers 5 and 6 on the switch.
The switch will now have 5 positions and can be installed.
Troubleshooting Steps
Checking the DSP5 Switch Voltage
Step 1:
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Connect the AutoCal or V2 to your truck and check the voltage of the DSP5 switch.
Note: If you are not familiar with this process follow the link below.
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If the voltage of the DSP5 switch is 4.1-5 volts with the switch on tune 1, and voltage drops
to 0.1-0.8v on tune 5 your switch is operating normally and the tunes are changing as they
should – no further troubleshooting is necessary.
If the voltage of the DSP5 switch is 4.1-5 volts with the switch on tune 1, and voltage does
not drop when selecting tunes 2, 3, 4, and 5 continue to step 2.
If the voltage for the DSP5 switch is 0 volts, full flash the DSP5 tune into the ECM.
Checking for Voltage at the DSP5 Switch
Step 2:
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Using a multi-meter, check for voltage at the red wire on the back of the switch.
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To do this, put the RED lead from the multi-meter on the soldered connection for the RED
wire on the back of the DSP5 switch, and the BLACK lead from the multi-meter to a good
body/chassis ground, or battery ground.
With the meter set to voltage, you should see 4.1-5v.
If you have 4.1-5v continue on to step 3. If you have 0v continue on to step 7.
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Checking for Resistance to Ground at the DSP5 Switch
Step 3:
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To do this, put one lead from the multi-meter (it doesn’t matter which one) to the soldered
connection of the BLACK wire at the back of the DSP5 switch, and the other lead to a good
body/chassis ground, or battery ground.
With the meter set to read ohms, you should see less than 5 ohms resistance. A good
ground will be less than 1 ohm.
If you have less than 5 ohms resistance, continue to step 4. If you have greater than 5 ohms
resistance go to step 6.
Step 4: Checking
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the Resistance of the DSP5 Switch
Check the resistance of the DSP5 switch. This is most accurately done by completely
disconnecting the switch from the truck so that the wires are no longer attached to the ECM
connector.
Using a multi-meter set to read ohms, put one lead on the soldered connection at the back
of the switch for the RED wire, and the other lead at the soldered connection for the BLACK
wire on the back of the switch. Set the switch to position 1.
Check the resistance of your switch against the values below*:
o Switch Position 1 - Tune 1: 25K ohms
o Switch Position 2 - Tune 2: 5.6K ohms
o Switch Position 3 - Tune 3: 2.2K ohms
o Switch Position 4 - Tune 4: 1.0K ohms
o Switch Position 5 - Tune 5: 270 ohms
* There is a slight tolerance on the above resistance values. Your readings may not be exactly
the same, but should be very close
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If the readings of your switch match above values, return to step 1 and data log the switch
again. If the readings of your switch do not match the values above, your switch is faulty
and must be replaced.
Step 5: Check the
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Step 6:
Resistance of the Red DSP5 Switch Wire
Using a multi-meter, check the resistance of the RED DSP5 switch wire from the pin at the
ECM to the back of the switch.
To do this set the multi-meter to read ohms, put one lead of the multi-meter at the
soldered connection for the RED wire at the back of the switch, and the other lead from the
multi-meter on the ECM pin on of the RED wire.
With the ECM pin installed in the ECM connector you may be able to back probe the pin
from the wire side. Or, you can insert a small wire into the ECM side of the connector,
making contact with the ECM pin.
The wiring should have less than 5 ohms resistance. A good wire will be less than 1 ohm.
If the wire tests below 5 ohms replace the ECM pin, if the wire tests above 5 ohms replace
the entire RED wire and pin.
Check the Resistance of the Black DSP5 Switch Wire
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Using a multi-meter, check the resistance of the BLACK DSP5 switch wire from the pin at the
ECM to the back of the switch. To do this set the multi-meter to read ohms, put one lead of
the multi-meter at the soldered connection for the BLACK wire at the back of the switch,
and the other lead from the multi-meter on the ECM pin on of the black wire.
With the ECM pin installed in the ECM connector you may be able to back probe the pin
from the wire side. Or, you can insert a small wire into the ECM side of the connector
making contact with the ECM pin.
The wiring should have less than 5 ohms resistance. A good wire will be less than 1 ohm.
If the wire tests below 5 ohms replace the ECM pin, if the wire tests above 5 ohms replace
the entire BLACK wire and pin.
Step 7: Checking
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DSP5 Switch Pin Installation
Check the installation of the DSP5 switch pins at the ECM. Closely inspect the following 3
things: The pins must be (1) in the correct pin location in the ECM, and (2) must be
completely seated. The ECM connector must (3) be completely seated into the ECM. If you
are unfamiliar with the switch installation process see the links below:
General installation video using an LBZ/LMM as an example:
- LBZ/LMM: Connector 1 (the larger plug) – RED (signal) at pin 46, and BLACK (ground) at pin 54.
- LLY: Grey connector – RED at pin 32, and BLACK at pin 50.
- LB7: Blue connector – RED at pin 69, and BLACK at pin 49
- If your switch wiring has been installed correctly go to step 5. If the switch has not
been installed correctly, reinstall the switch wiring per the instructions above.