Q: P0642 2006 Jeep Grand Cherokee

asked by on August 18, 2017

I am getting code p0642 along with u1408 and u140c. The U codes were able to be deleted but p0642 stays. It seems there is an issue with the 5 volt reference from what I've researched. What steps should I take before breaking off and buying new ecm?

My car has 138000 miles.
My car has an automatic transmission.

The low reference voltage may be from one of the engine sensors like the throttle position sensor shorted reference signal. You can try to disconnect one engine sensor at a time to see if code P0642 goes away and the sensor code may come up but if code Po642 goes away then you know that sensor is the shorted sensor. If after disconnecting sensors you continue to get the code P0642 then you will need to look at replacing the ECM.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Get an instant quote for your car

Our certified mechanics come to you ・Backed by 12-month, 12,000-mile guarantee・Fair and transparent pricing


Experienced Mechanic?

Earn up to $70/hr

What others are asking

How do I adjust the rearview mirror?
The rearview mirror is an important safety feature that provides you with visibility out your rear window. Before driving, you should always adjust your rearview mirror so that you have maximum visibility. To adjust the mirror, manually move it up,...
F-150 loses power while trying to go reverse
Fix your exhaust (https://www.yourmechanic.com/services/exhaust-system-hanger-replacement) and coil packs (https://www.yourmechanic.com/parts/ignition-coil) first, because if you'd want to get everything running right and your exhaust is leaking, that messes with your air flow out of the exhaust, which makes the oxygen sensors respond weirdly...
Alarm and keyless entry malfunction, G error code
Hey there, thanks for writing in about your 2007 Mercedes Benz E550. The car alarm in many of the later model Mercedes vehicles has it's own set of small batteries. When these batteries go bad, they will automatically set off the...
how do you know if you need a whole throttle body compared to just cleaning it or replacing sensors
I would recommend cleaning and replacing the sensors (https://www.yourmechanic.com/services/throttle-position-sensor-replacement) first. Generally, throttle bodies do not need to be replaced completely, but rather just need specific parts related to them replaced. I would also recommend checking the mass air flow sensor...
I had a leak in my lower radiator hose so I changed it. Now the car won't start now and the Check Engine Light is on.
Hello, lets start with the basics: since the Check Engine Light (https://www.yourmechanic.com/services/check-engine-light-is-on-inspection) is on, what problem codes are set? The codes are your friend - will make diagnosis much easier. Do you have spark at the spark plugs while cranking?...
2013 Dodge Grand Caravan codes P0123, P0222 and P0562...please help!!
P0123 (https://www.yourmechanic.com/article/p0123-obd-ii-trouble-code-throttle-pedal-position-sensor-switch-tps-a-circuit-high-input-by-jay-safford) and P0222 (https://www.yourmechanic.com/article/p0222-obd-ii-trouble-code-throttle-pedal-position-switch-sensor-b-circuit-low-input-by-andrew-quinn) both implicate the throttle position sensor and circuit. P0562 involves the charging circuit and alternator. These are not particularly difficult codes to resolve as both the charging circuit and the throttle position sensor/circuit can be...
Clutch failed and im unsure about if the slave cylinder seats in the transmission arm is still functional. 94 civic
This is normal for the clutch release arm to move side to side as it is in a ball joint and needs to pivot. As long as clutch is releasing properly now you should not have any worries.
When cooling fan turns on while driving the dash lights would flicker and rpm would drop then goes back to normal.
Nissan requires that the battery in 2004 Sentra's have a minimum CCA rating of 355 amps. Therefore, your battery is adequate, unless it has failed of course. If lights dim momentarily when the fans come on, that means that the...

Related articles

P2016 OBD-II Trouble Code: Intake Manifold Runner Position Sensor/Switch Circuit Low Bank 1
P2016 P2016 code definition Intake Manifold Runner Position Sensor/Switch Circuit Low Bank 1 What the P2016 code means P2016 is an OBD-II generic code for the Engine Control Module (ECM) detecting a low voltage failure in the intake manifold runner...
P003A OBD-II Trouble Code: Turbocharger/Supercharger Boost Control "A" Position Exceeded Learning Limit
The P003A trouble code means the Electronic Computer Module (ECM) has detected an issue in the turbocharger or supercharger system.
B2106 OBD-II Trouble Code: Throttle Position Input Out of Range High
B2106 trouble code means there's a range issue with the throttle position input in a 4WD system, caused by a damaged circuit in the 4WD system.