Evening Folks

Heres an interesting one, once a day, and perhaps once every 2 days or so I have been experiencing a wicked jolt shortly after starting the car. 

My initial thoughts were icy roads, slip under acceleration, lose forward momentum which gives me the jolt but the snow melted and it soon became apparent it was nothing to do with traction.

It seems to be under load that it happens at quite low RPM.

Today I managed to catch it on a trace using forscan and there was absolutely no indication of fuel rail problems, it was doing what it does without any obvious signs of a problem, turbo vanes doing their  thing fine, MAP and MAF all looking normal But then I looked at the torque trace and right at the moment of the jolt which this time physically threw my head forward a bit there was a massive spike to around 190Nm. Now my car normally hits this level at peak load but this was out of the blue

 

Anyhow, im open to suggestions, it will only happen once on any given day, fuel rail pressures are consistent, fuel filter changed about 2-3k ago I cant reproduce the problem, but it will happen once every 2-3 days.

Car has done 130K, she has some clutch slip under heavy acceleration which might explain a loss of power and thus some hesitation but ive experienced that before with a dodgy fuel sensor and this is nothing like it, id liken it to someone jumping in front of the car.  Ive added speed and brake PIDs to see if there is a visible change in speed and if the brakes engage but I thought id put it out here and see if anyone else has any ideas?

oh an no DTCs at all, no problems starting and runs fine before and after the jolt

 

 

I've noticed that my AC clutch is getting louder when engaging - does cycling the AC affect anything?

ill disable it and try it over the next couple of days and see if it changes anything but even if the AC pump fully locked up, id have thought the belt would just slip rather than throw that much force at the car..  ill see there is an effect. Cheers Ted

Low RPM under load sounds like ideal conditions for a bit of clutch slip tbh.  

That was my first thought shortly followed by the DMF but ive seen an felt clutch slip and this is less of a rock forward due to reduced acceleration with a corresponding increase in RPM and more of a proper kick in the chest deceleration and "clunk". 

So the mystery deepens I now have some DTCs this morning

Short on Crank sensor might have something to do with it which may have also effected the MAF. 

Anyone know if the Crank sensor and MAF are on the same loom?

Would a dodgy crank sensor cause that much of a jolt?

Is that -21 on P0335-21 the number of iterations of that error code, so has it flagged 21 times before it finally throw up a DTC?

 

 

===PCM DTC P0335-21===
Code: P0335 - CKP Sensor A Circuit

Additional Fault Symptom:
 - Signal is Above Maximum Threshold

Status: 
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

Diagnostic Trouble Code details

CKP Sensor A Circuit

This DTC may be caused by :

Open or Shorted CKP sensor circuit.

Suspect CKP sensor.

Wiring Harness Short to Battery or Short to Ground

Damaged or contaminated connector

Faulty or damaged PCM.

===END PCM DTC P0335-21===

===PCM DTC P0103-21===
Code: P0103 - MAF Sensor Circuit High Input

Additional Fault Symptom:
 - Signal is Above Maximum Threshold

Status: 
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

Diagnostic Trouble Code details

MAF Sensor Circuit High Input

This DTC is set when the MAF signal is higher than normal operating conditions.

This DTC may be caused by :

Signal shorted to VBATT or vref.

Damaged or contaminated connector

Faulty MAF sensor

open or short circuit

EGR System Fault

===END PCM DTC P0103-21===

===PCM DTC P0103-21===
Code: P0103 - MAF Sensor Circuit High Input

Additional Fault Symptom:
 - Signal is Above Maximum Threshold

Status: 
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Powertrain Control Module

Diagnostic Trouble Code details

MAF Sensor Circuit High Input

This DTC is set when the MAF signal is higher than normal operating conditions.

This DTC may be caused by :

Signal shorted to VBATT or vref.

Damaged or contaminated connector

Faulty MAF sensor

open or short circuit

EGR System Fault

===END PCM DTC P0103-21===

===FACM DTC None===
Successful DTC reading, no error codes found

Module: Fuel Additive Control Module

===END FACM DTC None===

===ABS DTC U2023-A0===
Code: U2023 - Vehicle Communication Network Fault

Status: 
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is On for this DTC

Module: Antilock braking system

Diagnostic Trouble Code details

Vehicle Communication Network Fault

CAN communication failure between the PCM and the ESP module.

This DTC may be caused by :

The ESP module has not received the correct message from other modules on the CAN communication data bus.

There may be other modules on the CAN communication data line that are not communicating and are timing out.

Short circuit on the CAN line.

Open circuit on the CAN line.

The ESP module has not received the correct message from other modules on the CAN communication data bus.

There is a time out between two modules on the CAN bus

There is Interference on the CAN bus

Perform these checks

Do not replace the ABS module based on this DTC alone. Make sure all the necessary checks have been carried out.

Check all connectors for continuity, corrosion, water ingress and any signs of visible damage.

Check that there are no CAN communication faults on the other modules.

Check the continuity of the CAN communication connections between the ABS and the PCM modules.

Check the wiring harness

Check the continuity of the CAN communication connections between the ABS module, other modules and the PCM.

Check the PCM for DTCs.

Note:

DTCs that start with 'U' are faults which occur during module-to-module communication.

Modules should never be replaced based only on a 'U' code. These codes do not always indicate a problem, and can be caused by normal diagnostic functions, carried out on the vehicle.

For further diagnostic information refer to the appropriate section of eTIS.

Additional Information

The ABS lamp should be illuminated.

The ESP lamp should be illuminated.

The ABS lamp should be illuminated.

There will be an ESP malfunction warning displayed on the driver information text panel.

===END ABS DTC U2023-A0===

===EPS DTC None===
Successful DTC reading, no error codes found

Module: Electronic-Controlled Power Steering

===END EPS DTC None===

===IC DTC U2196-20===
Code: U2196 - Invalid data for Engine RPM

Status: 
 - Previously Set DTC - Not Present at Time of Request
 - Malfunction Indicator Lamp is Off for this DTC

Module: Instrument Cluster

Diagnostic Trouble Code details

Invalid data for Engine RPM

Operator Action

Run self test.

All CMDTCs

Fix all relevant DTCs then clear codes and retest.

Note:

DTCs that start with 'U' are faults which occur during module-to-module communication.

Modules should never be replaced based only on a 'U' code. These codes do not always indicate a problem, and can be caused by normal diagnostic functions, carried out on the vehicle.

===END IC DTC U2196-20===

 

Sorry, on every other forum im on, inserting Code usually sticks in inside a box rather than fill up the thread with writing...

 

 

Soooo, we update on this, it got progressively worse, clapping out 3 or 4 times in succession, so I ended up taking a punt on it and changed the crank sensor, what a pain in the bum that thing is to get back in.  anyhow, after a lot of swearing I managed to slip it back in again, that was sunday, so far, no drama.  I dont want to count my chickens an all that but if its not fixed, then its certainly improved