2008 Chaparral 275 SSI 8.1 Volvo Penta GXI-J Soft Alarm Issues

[alldodge]

The sensor will look like this (this isn't yours)
https://www.amazon.com/Genuine-GM-12589867-Knock-Sensor/dp/B00F6768EY

 

[apisk]

The sensor will look like this (this isn't yours)
https://www.amazon.com/Genuine-GM-12589867-Knock-Sensor/dp/B00F6768EY

I was able to find that one on the bottom right side of the block, no wire interference but may be worth replacing as a just in case?

My main question around the 5V issue we are talking about is that according to the Diacom, it was low the entire time, what would make the alarm trigger past 3000RPM if the voltage was low the entire time? Is there a draw at that level that triggers it? I would think if the voltage was low, the alarm would always be going off?

 

[alldodge]

I wouldn't replace it unless there is more determination the motor does not have a knock, they normally don't go bad.

As tpenfield said the 5V is a critical reference point for the ECM, if it's off so is every other reading it gets. To find the sensor that is drawing to much current disconnect each sensor one at a time while measuring 5V circuit. This is done motor off key on

 

[apisk]

I wouldn't replace it unless there is more determination the motor does not have a knock, they normally don't go bad.

As tpenfield said the 5V is a critical reference point for the ECM, if it's off so is every other reading it gets. To find the sensor that is drawing to much current disconnect each sensor one at a time while measuring 5V circuit. This is done motor off key on

Is there a full list of all the sensors and their locations anywhere?

What is the best way to measure the 5V circuit as I undo each sensor?

 

[tpenfield]

You probably need the service Volvo-Penta manual for your engine.

A DVM (multimeter) would be useful in measuring the voltage as you continue diagnostics. (Also get some alligator clip leads)

 

[alldodge]

Don't exactly where they are, and 5V can be read from any of them. Connect to which ever is easiest to get to. Might also be able to see the voltage with diacom

Crank shaft CPS
Cam shaft sensor
Manifold Air and Temp MAP/T
Coolant Temp ECT
Oil pressure
TPS

Sea water pressure (Don't know for sure if VP uses this one)

 

[apisk]

You probably need the service Volvo-Penta manual for your engine.

A DVM (multimeter) would be useful in measuring the voltage as you continue diagnostics. (Also get some alligator clip leads)

Electrical is definitely not my strongest area, but I think I have identified all of the sensors and their locations - how do I go about measuring a 5V circuit as @alldodge mentioned? I don't think the Diacom was reading the volts for each sensor. Am I hooking up the alligator clip leads to the wiring for each sensor to check the volts, or is there somewhere else I hook up to and then unplug each sensor to see when the readings change? Apologies if this is a bit amateur but want to make sure I understand fully

 

[apisk]

I was able to get a hold of the wiring diagram, and traced back the 5V Reference 2 to the "TCP Sensor" - what is that? Did I read this correct?

Link to wiring diagram in case the attachment doesn't load

volvo penta 8.1 gxi-j wiring diagram.pdf

drive.google.com

 

[tpenfield]

Throttle Control Position

 

[alldodge]

Electrical is definitely not my strongest area, but I think I have identified all of the sensors and their locations - how do I go about measuring a 5V circuit as @alldodge mentioned? I don't think the Diacom was reading the volts for each sensor. Am I hooking up the alligator clip leads to the wiring for each sensor to check the volts, or is there somewhere else I hook up to and then unplug each sensor to see when the readings change? Apologies if this is a bit amateur but want to make sure I understand fully

Take any one of the sensors and attach the meter.
OR
Connect Diacom and see if it will read the 5V without the motor running

Either way once you can see the 5V reference voltage then start unplugging one at a time. If it doesn't go up to full 5V, plug sensor back in and go to next sensor

 

[apisk]

Take any one of the sensors and attach the meter.
OR
Connect Diacom and see if it will read the 5V without the motor running

Either way once you can see the 5V reference voltage then start unplugging one at a time. If it doesn't go up to full 5V, plug sensor back in and go to next sensor

I connected Diacom without the motor running and it read the 5V. The Reference 2 was reading at 4.16. I started with the TCP sensor, unplugged that and it jumped up to 4.98 immediately

 

[alldodge]

keep going

 

[apisk]

I unplugged every other sensor, the 5V reading didn't change for any of them, the only time it changed was the TCP where it jumped up to 4.98

 

[alldodge]

Guess you found the problem child

 

[tpenfield]

OK - So, you will probably be replacing the TCP sensor and then seeing if the soft alarm goes away. If it does not, then see if you have the same characteristic with the Knock Sensor & Knock Retard readings on a trial run.

Some of the prices of the V-P sensors are a little scary . . . but there may be GM equivalents at a more reasonable price. I usually try to get a part number off the old sensor to cross reference them to the generic part.

 

[apisk]

Thank you both @alldodge and @tpenfield - I ordered a replacement TCP sensor that is hopefully coming tomorrow. Once replaced I will update the thread with my findings. Really appreciate both of your help

 

[apisk]

Just replaced the TCP sensor, and before taking it for a test drive the 5V ref 2 is still reading 4.10. When I unplug it, the value jumps back up to 5 as expected. What else could be causing this if the TCP sensor is brand new? Is there a bad wire in the feed from the sensor to the ECM?

 

[alldodge]

Has to be something with it, as you said in post 53, nothing changed with others

This is how they are wired

 

[apisk]

Sorry, when you say "it" do you mean the new sensor? I can say with 100% confidence no other sensor caused any changes in the 5V reading when I unplugged them

 

[alldodge]

The connection to the new sensor

Does the voltage change when TPS is moved from idle to WOT?