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Code P242D - Exhaust Temp Sensor

12K views 5 replies 2 participants last post by  OR Mega Cab  
#1 · (Edited)
Hi All,

So I have been having the P242D code off and on for a couple weeks. I figured out on Alpha OBD that you can graph the temp sensor outputs in real time for all 5 exhaust temp sensors on my 2013. After graphing them, see pics, it became obvious something was up with sensor 3. When working correctly it will display similar temps to sensors 2 & 4. Then randomly Sensor 3 will shoot up to 2900 deg C or down to 5 deg C, I know neither of which is possible. I figured this indicated a faulty sensor. Picked up a new temp sensor and replaced it. Same thing still happens with graph & code. I replaced the sensor on the rear side of the DPF. I am fairly certain this is sensor 3 on a 2013. Next step I am going to upplug this sensor and go for a drive and watch the graphs on Alpha OBD to verify I replaced the correct sensor. Assuming I have replaced the correct sensor, what else would cause the output from the sensor to spike like it is? Truck is stock, 190K miles.

Thanks!
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#2 ·
Bad wire or connection. There was a wiring recall done on that year truck involving the order of the plugs. They reordered what plugged to what and also changed parts of the harness. You may have a short in the harness.

2013 2500 6.7 cummins crew cab. white and stock as can be
using Tapatalk
 
#3 ·
Bad wire or connection. There was a wiring recall done on that year truck involving the order of the plugs. They reordered what plugged to what and also changed parts of the harness. You may have a short in the harness.

2013 2500 6.7 cummins crew cab. white and stock as can be
using Tapatalk
Thanks for the info. I noticed the wire was stretched really tight for sensor 2 when I was under the truck checking everything and replacing sensor 3 and the mounting brackets for sensors 2&3 were broken off the frame. Both would make sense if they had been switched as part of a recall years ago. I looked the wires over really closely yesterday with a flashlight all the way from sensor 5 to the fusebox under the hood and was unable to locate and visible chafing. I did reroute some of the sensor wiring that was tight around sensors 2&3 and went for a couple drives yesterday and no codes thrown and temp graph was smooth like expected. I'm thinking playing with the wires pushed a short back together, so probably a temporary repair. Hopefully I am on to something with the wiring down by sensors 2 & 3.

Thanks for your help!
 
#5 ·
Have you tried cleaning the plug terminals with connector cleaner? They may just be making a bad connection.
I do believe the entire repair is done where you see all of the wires enter into the harness on the frame rail next to the exhaust filters. I know the recall has a tsb for it but don't remember which is was. I do know it was done before 2017 tho as that was the last I let them do recall work.

2013 2500 6.7 cummins crew cab. white and stock as can be
using Tapatalk
 
#6 ·
Thanks. Cleaned connectors still getting random P242D Code.
Investigating the ECM area today.


Does anyone know if the Theory of Operation I found for a 2008 6.7 is the same for my 2013 6.7?

P242D Theory of Operation:

The Exhaust Temperature Sensors are used by the Electronic Control Module (ECM) to monitor the engine exhaust temperatures in the aftertreatment system. The Exhaust Temperature Sensors are thermistors and change resistance based on the temperature being measured. The ECM provides a 5-volt reference voltage to the sensor. The ECM monitors the change in signal voltage and converts this to a temperature value. When the exhaust gas temperature is cold, the sensor or thermistor resistance is high. The ECM signal voltage only pulls down a small amount through the sensor to ground. Therefore, the ECM senses a high signal voltage or low temperature. When
the exhaust gas temperature is hot, the sensor resistance is low. The signal voltage pulls down a large amount. Therefore, the ECM senses a low signal voltage, or a high temperature. The ECM will set the fault if it detects that
the diesel oxidation catalyst inlet exhaust gas temperature sensor signal voltage is greater than a calibrated voltage for more than a calibrated time. The ECM illuminates the MIL lamp immediately when the diagnostic runs and fails. A default value for the Exhaust Temperature Sensor 1/1 reading will be used and active regeneration of the diesel particulate filter will be disabled. The ECM will turn off the MIL lamp immediately after the diagnostic runs and
passes.

When Monitored:
When ignition switch is ON

Set Condition:
The ECM will set the fault if it detects that the Exhaust Temperature Sensor Signal voltage is greater than a calibrated voltage for more than a calibrated time.

Possible Causes:
FAILED SENSOR
(K372) EXHAUST TEMPERATURE 1/3 SIGNAL CIRCUIT OPEN
(K900) SENSOR GROUND CIRCUIT OPEN
(K372) EXHAUST TEMPERATURE 1/3 SIGNAL CIRCUIT SHORTED TO VOLTAGE
(K372) EXHAUST TEMPERATURE 1/3 SIGNAL CIRCUIT SHORTED TO OTHER CIRCUITS
ECM

Diagnostic Tests:

1. TEMPERATURE SENSOR CHECK.
Disconnect the Exhaust Temperature Sensor 1/3. NOTE: Check connectors - Clean/repair as necessary. Using an ohmmeter check the resistance of the sensor. NOTE: The sensor’s resistance value increases with decreasing temperature @ 50° C (122° F) resistance ranges from 82k to 137k ohms. Is the resistance between 82k and 300k ohms at ambient temperature?

Yes >> Go To 2
No >> Replace the sensor

2. EXHAUST TEMPERATURE SENSOR 1/3 CIRCUIT CHECK.
Reconnect the Temperature sensor. Disconnect the (Connector 2) engine ECM sensor harness connector. NOTE: Check connectors - Clean/repair as necessary. Measure the resistance between the (K372 brown/dark green wire in pin 10 of the ecm connector) Exhaust Temperature 1/3 Signal circuit and (K900 dark blue/dark green wire in pin 20 of the ecm connector) Sensor ground circuit at the ECM harness connector. Is the resistance between 82k and 300k ohms at ambient temperature?

Yes >> Go To 5
No >> Go To 3

3. (K372) EXHAUST TEMPERATURE 1/3 SIGNAL CIRCUIT OPEN CHECK.
Disconnect the Exhaust Temperature Sensor 1/3 Measure the resistance of the (K372 brown/dark green wire in pin 1 of the exhaust temperature sensor connector) Exhaust Temperature 1/3 Signal circuit between the sensor harness connector and the ECM harness connector pin 10. Is the resistance less than 10 Ohms?

Yes >> Go To 4
No >> Repair the open in the (K372) Exhaust Temperature 1/3 Signal circuit.

4. (K900) SENSOR GROUND CIRCUIT OPEN CHECK.
Measure the resistance of the (K900 dark blue/dark green wire in pin 2 of the exhaust temperature sensor connector) Sensor ground circuit between the Exhaust Temperature 1/3 Sensor harness connector and the ECM harness connector pin 20. Is the resistance less than 10 Ohms?

Yes >> Go To
No >> Repair the open in the (K900) Sensor ground circuit.

5. (K372) EXHAUST TEMPERATURE 1/3 SIGNAL CIRCUIT SHORTED TO ANOTHER CIRCUIT CHECK.
Measure resistance between the (K372 brown/dark green pin 10) Exhaust Temperature 1/3 Signal circuit and all other circuits at the ECM harness connector. Is the resistance more than 100 k ohms?

Yes >> Go to 6
No >> Repair the circuits that are shorted together.

6. ECM logic check.
Reconnect the ECM harness connector. While monitoring the Exhaust Temperature Sensor 1/3 with scan tool, use a jumper wire and connect the (K372) Exhaust Temperature 1/3 Signal circuit to the (K900) Sensor ground at the sensor connector. Did the DTC for voltage high go inactive and the DTC for voltage low become active?
Yes >> Fault is intermittent & will have to be readily duplicated to troubleshoot further.
No >> Replace the ECM.