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No Bus code

Tiny
RON VAN D
  • MEMBER
  • 2002 DODGE DAKOTA
  • 4.7L
  • V8
  • 172,000 MILES
I have a no BUS code in odometer truck wont start unless you leave the key on after about 10 to 15 minutes no BUS goes away and the engine runs normally. Have changed the speed sensor and the crankshaft position sensor, checked fuses and the wiring for weak spots and rub marks. Removed the fuse panel to look at the connections. Checked the ground straps unplugged the PCM to look for corrosion. Checked the voltage at the sensor connections. I can't find anything. I need help to figure this out.
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Wednesday, July 10th, 2019 AT 9:10 AM

13 Replies

Tiny
ASEMASTER6371
  • MECHANIC
  • 52,797 POSTS
Good afternoon,

What is the code number?

Roy
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Wednesday, July 10th, 2019 AT 12:26 PM
Tiny
RON VAN D
  • MEMBER
  • 13 POSTS
I will have to look but I am pretty sure it says nobus in the odometer. It may be nobu5.
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Wednesday, July 10th, 2019 AT 2:18 PM
Tiny
ASEMASTER6371
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I need the code from the PCM. It will be a code that starts with a P and then some numbers.

Roy
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Wednesday, July 10th, 2019 AT 2:22 PM
Tiny
RON VAN D
  • MEMBER
  • 13 POSTS
I checked the PCM with a code reader there are no codes logged in the PCM that is why I am having such a tough time trying to figure it out what is wrong.
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Thursday, July 11th, 2019 AT 1:32 PM
Tiny
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Okay, do you have a scan tool that can read the instrument cluster?

See if you can see the miles in the cluster on the scan tool.

Roy
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Thursday, July 11th, 2019 AT 2:16 PM
Tiny
RON VAN D
  • MEMBER
  • 13 POSTS
Okay, so I plugged in the scanner it wont read miles but I hit OEM enhansed scan and am getting po725 I just put a new engine speed sensor in the transmission cleared the code this was about two weeks ago but the code has returned. The scanner. Says the code is for the transmission control module is not that the same as that speed sensor I replaced or is that something else. Also I was in the fuse panel an noticed a relay for the transmission it seemed a little warmer than the rest. Is that normal?
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Thursday, July 11th, 2019 AT 5:18 PM
Tiny
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No, the module is not the same as the sensor.

The code is for engine speed sensor which is the crankshaft position sensor.

Below is the possible issue and a flow chart for you to follow.

Roy

P0725
Descriptor
Engine Speed Sensor Circuit
Probable Causes
Crankshaft Position (CKP) Sensor Signal Circuit Open to Transmission Control Module (TCM)
Intermittent Wiring and Connectors
Related Powertrain Control Module (PCM) Diagnostic Trouble Codes (DTC's) Present
Sensor Ground Circuit Open to Transmission Control Module (TCM)
Transmission Control Module (TCM) Engine Speed Sensor Circuit

More information

SYMPTOM
P0725 - ENGINE SPEED SENSOR CIRCUIT

WHEN MONITORED
Continuously with engine running.

SET CONDITION
This code is set when the engine speed sensed by the Transmission Control Module (TCM) is less than 400 rpm and the engine is running (As reported by the PCM over the communication bus) for 2 seconds. This DTC can take up to five minutes of problem identification before illuminating the MIL.

POSSIBLE CAUSES
- Related PCM DTC's present
- Intermittent wiring and connectors
- CKP signal circuit open to TCM
- Sensor ground circuit open to TCM
- TCM - Engine speed sensor circuit
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Thursday, July 11th, 2019 AT 5:28 PM
Tiny
RON VAN D
  • MEMBER
  • 13 POSTS
Okay, I have replaced the crankshaft. So if I can get u to walk me threw it position sensor as well as the engine speed sensor what would you recommend next? I read over the information you sent, it is a little hard for me to get my head around it. I know quite a bit but is all old school.
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Thursday, July 11th, 2019 AT 5:59 PM
Tiny
ASEMASTER6371
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Replaced the crankshaft? Please explain?

The sensor is at the lower end of the passenger side of the engine. It is easier to get it from the bottom. It has one bolt securing it. Remove the bolt, remove the connector and twist the sensor to release the o ring and remove.

If that is the issue, the code will go away.

The crank sensor is the speed sensor. They are the same.

Roy
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Thursday, July 11th, 2019 AT 6:03 PM
Tiny
RON VAN D
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I replaced the crank sensor already but it did no good. I also replaced the engine speed sensor on the transmission located on the left side of the transmission.
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Thursday, July 11th, 2019 AT 7:17 PM
Tiny
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Okay, that's the output speed sensor.

You need to go back to the flow chart I posted and follow the chart.

Roy
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Thursday, July 11th, 2019 AT 7:29 PM
Tiny
RON VAN D
  • MEMBER
  • 13 POSTS
Thanks Roy. I tried to follow the flow chart, but it is too technical for me. Sorry. Any other information or a break down of the flow chart to simpler terms so I can understand what it is trying to show me?
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Tuesday, July 16th, 2019 AT 9:42 AM
Tiny
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You are going to need some outside help if you do not understand. This is what a tech does all day long when they do diagnostics.

I would at least let someone do the diagnostic for you then you can do the repair.

Roy
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Tuesday, July 16th, 2019 AT 9:47 AM

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